Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | /* |
| 2 | * Fast Userspace Mutexes (which I call "Futexes!"). |
| 3 | * (C) Rusty Russell, IBM 2002 |
| 4 | * |
| 5 | * Generalized futexes, futex requeueing, misc fixes by Ingo Molnar |
| 6 | * (C) Copyright 2003 Red Hat Inc, All Rights Reserved |
| 7 | * |
| 8 | * Removed page pinning, fix privately mapped COW pages and other cleanups |
| 9 | * (C) Copyright 2003, 2004 Jamie Lokier |
| 10 | * |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 11 | * Robust futex support started by Ingo Molnar |
| 12 | * (C) Copyright 2006 Red Hat Inc, All Rights Reserved |
| 13 | * Thanks to Thomas Gleixner for suggestions, analysis and fixes. |
| 14 | * |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 15 | * PI-futex support started by Ingo Molnar and Thomas Gleixner |
| 16 | * Copyright (C) 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com> |
| 17 | * Copyright (C) 2006 Timesys Corp., Thomas Gleixner <tglx@timesys.com> |
| 18 | * |
Eric Dumazet | 34f01cc | 2007-05-09 02:35:04 -0700 | [diff] [blame] | 19 | * PRIVATE futexes by Eric Dumazet |
| 20 | * Copyright (C) 2007 Eric Dumazet <dada1@cosmosbay.com> |
| 21 | * |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 22 | * Requeue-PI support by Darren Hart <dvhltc@us.ibm.com> |
| 23 | * Copyright (C) IBM Corporation, 2009 |
| 24 | * Thanks to Thomas Gleixner for conceptual design and careful reviews. |
| 25 | * |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 26 | * Thanks to Ben LaHaise for yelling "hashed waitqueues" loudly |
| 27 | * enough at me, Linus for the original (flawed) idea, Matthew |
| 28 | * Kirkwood for proof-of-concept implementation. |
| 29 | * |
| 30 | * "The futexes are also cursed." |
| 31 | * "But they come in a choice of three flavours!" |
| 32 | * |
| 33 | * This program is free software; you can redistribute it and/or modify |
| 34 | * it under the terms of the GNU General Public License as published by |
| 35 | * the Free Software Foundation; either version 2 of the License, or |
| 36 | * (at your option) any later version. |
| 37 | * |
| 38 | * This program is distributed in the hope that it will be useful, |
| 39 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 40 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 41 | * GNU General Public License for more details. |
| 42 | * |
| 43 | * You should have received a copy of the GNU General Public License |
| 44 | * along with this program; if not, write to the Free Software |
| 45 | * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA |
| 46 | */ |
| 47 | #include <linux/slab.h> |
| 48 | #include <linux/poll.h> |
| 49 | #include <linux/fs.h> |
| 50 | #include <linux/file.h> |
| 51 | #include <linux/jhash.h> |
| 52 | #include <linux/init.h> |
| 53 | #include <linux/futex.h> |
| 54 | #include <linux/mount.h> |
| 55 | #include <linux/pagemap.h> |
| 56 | #include <linux/syscalls.h> |
Jesper Juhl | 7ed20e1 | 2005-05-01 08:59:14 -0700 | [diff] [blame] | 57 | #include <linux/signal.h> |
Paul Gortmaker | 9984de1 | 2011-05-23 14:51:41 -0400 | [diff] [blame] | 58 | #include <linux/export.h> |
Andrey Mirkin | fd5eea4 | 2007-10-16 23:30:13 -0700 | [diff] [blame] | 59 | #include <linux/magic.h> |
Pavel Emelyanov | b488893 | 2007-10-18 23:40:14 -0700 | [diff] [blame] | 60 | #include <linux/pid.h> |
| 61 | #include <linux/nsproxy.h> |
Kees Cook | bdbb776 | 2012-03-19 16:12:53 -0700 | [diff] [blame] | 62 | #include <linux/ptrace.h> |
Clark Williams | 8bd75c7 | 2013-02-07 09:47:07 -0600 | [diff] [blame] | 63 | #include <linux/sched/rt.h> |
Zhang Yi | 13d60f4 | 2013-06-25 21:19:31 +0800 | [diff] [blame] | 64 | #include <linux/hugetlb.h> |
Colin Cross | 88c8004 | 2013-05-01 18:35:05 -0700 | [diff] [blame] | 65 | #include <linux/freezer.h> |
Davidlohr Bueso | a52b89e | 2014-01-12 15:31:23 -0800 | [diff] [blame] | 66 | #include <linux/bootmem.h> |
Pavel Emelyanov | b488893 | 2007-10-18 23:40:14 -0700 | [diff] [blame] | 67 | |
Jakub Jelinek | 4732efb | 2005-09-06 15:16:25 -0700 | [diff] [blame] | 68 | #include <asm/futex.h> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 69 | |
Peter Zijlstra | 1696a8b | 2013-10-31 18:18:19 +0100 | [diff] [blame] | 70 | #include "locking/rtmutex_common.h" |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 71 | |
Thomas Gleixner | 99b60ce | 2014-01-12 15:31:24 -0800 | [diff] [blame] | 72 | /* |
| 73 | * Basic futex operation and ordering guarantees: |
| 74 | * |
| 75 | * The waiter reads the futex value in user space and calls |
| 76 | * futex_wait(). This function computes the hash bucket and acquires |
| 77 | * the hash bucket lock. After that it reads the futex user space value |
Davidlohr Bueso | b0c29f7 | 2014-01-12 15:31:25 -0800 | [diff] [blame] | 78 | * again and verifies that the data has not changed. If it has not changed |
| 79 | * it enqueues itself into the hash bucket, releases the hash bucket lock |
| 80 | * and schedules. |
Thomas Gleixner | 99b60ce | 2014-01-12 15:31:24 -0800 | [diff] [blame] | 81 | * |
| 82 | * The waker side modifies the user space value of the futex and calls |
Davidlohr Bueso | b0c29f7 | 2014-01-12 15:31:25 -0800 | [diff] [blame] | 83 | * futex_wake(). This function computes the hash bucket and acquires the |
| 84 | * hash bucket lock. Then it looks for waiters on that futex in the hash |
| 85 | * bucket and wakes them. |
Thomas Gleixner | 99b60ce | 2014-01-12 15:31:24 -0800 | [diff] [blame] | 86 | * |
Davidlohr Bueso | b0c29f7 | 2014-01-12 15:31:25 -0800 | [diff] [blame] | 87 | * In futex wake up scenarios where no tasks are blocked on a futex, taking |
| 88 | * the hb spinlock can be avoided and simply return. In order for this |
| 89 | * optimization to work, ordering guarantees must exist so that the waiter |
| 90 | * being added to the list is acknowledged when the list is concurrently being |
| 91 | * checked by the waker, avoiding scenarios like the following: |
Thomas Gleixner | 99b60ce | 2014-01-12 15:31:24 -0800 | [diff] [blame] | 92 | * |
| 93 | * CPU 0 CPU 1 |
| 94 | * val = *futex; |
| 95 | * sys_futex(WAIT, futex, val); |
| 96 | * futex_wait(futex, val); |
| 97 | * uval = *futex; |
| 98 | * *futex = newval; |
| 99 | * sys_futex(WAKE, futex); |
| 100 | * futex_wake(futex); |
| 101 | * if (queue_empty()) |
| 102 | * return; |
| 103 | * if (uval == val) |
| 104 | * lock(hash_bucket(futex)); |
| 105 | * queue(); |
| 106 | * unlock(hash_bucket(futex)); |
| 107 | * schedule(); |
| 108 | * |
| 109 | * This would cause the waiter on CPU 0 to wait forever because it |
| 110 | * missed the transition of the user space value from val to newval |
| 111 | * and the waker did not find the waiter in the hash bucket queue. |
Thomas Gleixner | 99b60ce | 2014-01-12 15:31:24 -0800 | [diff] [blame] | 112 | * |
Davidlohr Bueso | b0c29f7 | 2014-01-12 15:31:25 -0800 | [diff] [blame] | 113 | * The correct serialization ensures that a waiter either observes |
| 114 | * the changed user space value before blocking or is woken by a |
| 115 | * concurrent waker: |
| 116 | * |
| 117 | * CPU 0 CPU 1 |
Thomas Gleixner | 99b60ce | 2014-01-12 15:31:24 -0800 | [diff] [blame] | 118 | * val = *futex; |
| 119 | * sys_futex(WAIT, futex, val); |
| 120 | * futex_wait(futex, val); |
Davidlohr Bueso | b0c29f7 | 2014-01-12 15:31:25 -0800 | [diff] [blame] | 121 | * |
| 122 | * waiters++; |
| 123 | * mb(); (A) <-- paired with -. |
| 124 | * | |
| 125 | * lock(hash_bucket(futex)); | |
| 126 | * | |
| 127 | * uval = *futex; | |
| 128 | * | *futex = newval; |
| 129 | * | sys_futex(WAKE, futex); |
| 130 | * | futex_wake(futex); |
| 131 | * | |
| 132 | * `-------> mb(); (B) |
Thomas Gleixner | 99b60ce | 2014-01-12 15:31:24 -0800 | [diff] [blame] | 133 | * if (uval == val) |
Davidlohr Bueso | b0c29f7 | 2014-01-12 15:31:25 -0800 | [diff] [blame] | 134 | * queue(); |
Thomas Gleixner | 99b60ce | 2014-01-12 15:31:24 -0800 | [diff] [blame] | 135 | * unlock(hash_bucket(futex)); |
Davidlohr Bueso | b0c29f7 | 2014-01-12 15:31:25 -0800 | [diff] [blame] | 136 | * schedule(); if (waiters) |
| 137 | * lock(hash_bucket(futex)); |
| 138 | * wake_waiters(futex); |
| 139 | * unlock(hash_bucket(futex)); |
| 140 | * |
| 141 | * Where (A) orders the waiters increment and the futex value read -- this |
| 142 | * is guaranteed by the head counter in the hb spinlock; and where (B) |
| 143 | * orders the write to futex and the waiters read -- this is done by the |
| 144 | * barriers in get_futex_key_refs(), through either ihold or atomic_inc, |
| 145 | * depending on the futex type. |
| 146 | * |
| 147 | * This yields the following case (where X:=waiters, Y:=futex): |
| 148 | * |
| 149 | * X = Y = 0 |
| 150 | * |
| 151 | * w[X]=1 w[Y]=1 |
| 152 | * MB MB |
| 153 | * r[Y]=y r[X]=x |
| 154 | * |
| 155 | * Which guarantees that x==0 && y==0 is impossible; which translates back into |
| 156 | * the guarantee that we cannot both miss the futex variable change and the |
| 157 | * enqueue. |
Thomas Gleixner | 99b60ce | 2014-01-12 15:31:24 -0800 | [diff] [blame] | 158 | */ |
| 159 | |
Heiko Carstens | 03b8c7b | 2014-03-02 13:09:47 +0100 | [diff] [blame^] | 160 | #ifndef CONFIG_HAVE_FUTEX_CMPXCHG |
Thomas Gleixner | a0c1e90 | 2008-02-23 15:23:57 -0800 | [diff] [blame] | 161 | int __read_mostly futex_cmpxchg_enabled; |
Heiko Carstens | 03b8c7b | 2014-03-02 13:09:47 +0100 | [diff] [blame^] | 162 | #endif |
Thomas Gleixner | a0c1e90 | 2008-02-23 15:23:57 -0800 | [diff] [blame] | 163 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 164 | /* |
Darren Hart | b41277d | 2010-11-08 13:10:09 -0800 | [diff] [blame] | 165 | * Futex flags used to encode options to functions and preserve them across |
| 166 | * restarts. |
| 167 | */ |
| 168 | #define FLAGS_SHARED 0x01 |
| 169 | #define FLAGS_CLOCKRT 0x02 |
| 170 | #define FLAGS_HAS_TIMEOUT 0x04 |
| 171 | |
| 172 | /* |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 173 | * Priority Inheritance state: |
| 174 | */ |
| 175 | struct futex_pi_state { |
| 176 | /* |
| 177 | * list of 'owned' pi_state instances - these have to be |
| 178 | * cleaned up in do_exit() if the task exits prematurely: |
| 179 | */ |
| 180 | struct list_head list; |
| 181 | |
| 182 | /* |
| 183 | * The PI object: |
| 184 | */ |
| 185 | struct rt_mutex pi_mutex; |
| 186 | |
| 187 | struct task_struct *owner; |
| 188 | atomic_t refcount; |
| 189 | |
| 190 | union futex_key key; |
| 191 | }; |
| 192 | |
Darren Hart | d8d88fb | 2009-09-21 22:30:30 -0700 | [diff] [blame] | 193 | /** |
| 194 | * struct futex_q - The hashed futex queue entry, one per waiting task |
Randy Dunlap | fb62db2 | 2010-10-13 11:02:34 -0700 | [diff] [blame] | 195 | * @list: priority-sorted list of tasks waiting on this futex |
Darren Hart | d8d88fb | 2009-09-21 22:30:30 -0700 | [diff] [blame] | 196 | * @task: the task waiting on the futex |
| 197 | * @lock_ptr: the hash bucket lock |
| 198 | * @key: the key the futex is hashed on |
| 199 | * @pi_state: optional priority inheritance state |
| 200 | * @rt_waiter: rt_waiter storage for use with requeue_pi |
| 201 | * @requeue_pi_key: the requeue_pi target futex key |
| 202 | * @bitset: bitset for the optional bitmasked wakeup |
| 203 | * |
| 204 | * We use this hashed waitqueue, instead of a normal wait_queue_t, so |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 205 | * we can wake only the relevant ones (hashed queues may be shared). |
| 206 | * |
| 207 | * A futex_q has a woken state, just like tasks have TASK_RUNNING. |
Pierre Peiffer | ec92d08 | 2007-05-09 02:35:00 -0700 | [diff] [blame] | 208 | * It is considered woken when plist_node_empty(&q->list) || q->lock_ptr == 0. |
Randy Dunlap | fb62db2 | 2010-10-13 11:02:34 -0700 | [diff] [blame] | 209 | * The order of wakeup is always to make the first condition true, then |
Darren Hart | d8d88fb | 2009-09-21 22:30:30 -0700 | [diff] [blame] | 210 | * the second. |
| 211 | * |
| 212 | * PI futexes are typically woken before they are removed from the hash list via |
| 213 | * the rt_mutex code. See unqueue_me_pi(). |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 214 | */ |
| 215 | struct futex_q { |
Pierre Peiffer | ec92d08 | 2007-05-09 02:35:00 -0700 | [diff] [blame] | 216 | struct plist_node list; |
Darren Hart | d8d88fb | 2009-09-21 22:30:30 -0700 | [diff] [blame] | 217 | |
Thomas Gleixner | f1a11e0 | 2009-05-05 19:21:40 +0200 | [diff] [blame] | 218 | struct task_struct *task; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 219 | spinlock_t *lock_ptr; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 220 | union futex_key key; |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 221 | struct futex_pi_state *pi_state; |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 222 | struct rt_mutex_waiter *rt_waiter; |
Darren Hart | 84bc4af | 2009-08-13 17:36:53 -0700 | [diff] [blame] | 223 | union futex_key *requeue_pi_key; |
Thomas Gleixner | cd68998 | 2008-02-01 17:45:14 +0100 | [diff] [blame] | 224 | u32 bitset; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 225 | }; |
| 226 | |
Darren Hart | 5bdb05f | 2010-11-08 13:40:28 -0800 | [diff] [blame] | 227 | static const struct futex_q futex_q_init = { |
| 228 | /* list gets initialized in queue_me()*/ |
| 229 | .key = FUTEX_KEY_INIT, |
| 230 | .bitset = FUTEX_BITSET_MATCH_ANY |
| 231 | }; |
| 232 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 233 | /* |
Darren Hart | b2d0994 | 2009-03-12 00:55:37 -0700 | [diff] [blame] | 234 | * Hash buckets are shared by all the futex_keys that hash to the same |
| 235 | * location. Each key may have multiple futex_q structures, one for each task |
| 236 | * waiting on a futex. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 237 | */ |
| 238 | struct futex_hash_bucket { |
Pierre Peiffer | ec92d08 | 2007-05-09 02:35:00 -0700 | [diff] [blame] | 239 | spinlock_t lock; |
| 240 | struct plist_head chain; |
Davidlohr Bueso | a52b89e | 2014-01-12 15:31:23 -0800 | [diff] [blame] | 241 | } ____cacheline_aligned_in_smp; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 242 | |
Davidlohr Bueso | a52b89e | 2014-01-12 15:31:23 -0800 | [diff] [blame] | 243 | static unsigned long __read_mostly futex_hashsize; |
| 244 | |
| 245 | static struct futex_hash_bucket *futex_queues; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 246 | |
Davidlohr Bueso | b0c29f7 | 2014-01-12 15:31:25 -0800 | [diff] [blame] | 247 | static inline void futex_get_mm(union futex_key *key) |
| 248 | { |
| 249 | atomic_inc(&key->private.mm->mm_count); |
| 250 | /* |
| 251 | * Ensure futex_get_mm() implies a full barrier such that |
| 252 | * get_futex_key() implies a full barrier. This is relied upon |
| 253 | * as full barrier (B), see the ordering comment above. |
| 254 | */ |
| 255 | smp_mb__after_atomic_inc(); |
| 256 | } |
| 257 | |
| 258 | static inline bool hb_waiters_pending(struct futex_hash_bucket *hb) |
| 259 | { |
| 260 | #ifdef CONFIG_SMP |
| 261 | /* |
| 262 | * Tasks trying to enter the critical region are most likely |
| 263 | * potential waiters that will be added to the plist. Ensure |
| 264 | * that wakers won't miss to-be-slept tasks in the window between |
| 265 | * the wait call and the actual plist_add. |
| 266 | */ |
| 267 | if (spin_is_locked(&hb->lock)) |
| 268 | return true; |
| 269 | smp_rmb(); /* Make sure we check the lock state first */ |
| 270 | |
| 271 | return !plist_head_empty(&hb->chain); |
| 272 | #else |
| 273 | return true; |
| 274 | #endif |
| 275 | } |
| 276 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 277 | /* |
| 278 | * We hash on the keys returned from get_futex_key (see below). |
| 279 | */ |
| 280 | static struct futex_hash_bucket *hash_futex(union futex_key *key) |
| 281 | { |
| 282 | u32 hash = jhash2((u32*)&key->both.word, |
| 283 | (sizeof(key->both.word)+sizeof(key->both.ptr))/4, |
| 284 | key->both.offset); |
Davidlohr Bueso | a52b89e | 2014-01-12 15:31:23 -0800 | [diff] [blame] | 285 | return &futex_queues[hash & (futex_hashsize - 1)]; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 286 | } |
| 287 | |
| 288 | /* |
| 289 | * Return 1 if two futex_keys are equal, 0 otherwise. |
| 290 | */ |
| 291 | static inline int match_futex(union futex_key *key1, union futex_key *key2) |
| 292 | { |
Darren Hart | 2bc8720 | 2009-10-14 10:12:39 -0700 | [diff] [blame] | 293 | return (key1 && key2 |
| 294 | && key1->both.word == key2->both.word |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 295 | && key1->both.ptr == key2->both.ptr |
| 296 | && key1->both.offset == key2->both.offset); |
| 297 | } |
| 298 | |
Peter Zijlstra | 38d47c1 | 2008-09-26 19:32:20 +0200 | [diff] [blame] | 299 | /* |
| 300 | * Take a reference to the resource addressed by a key. |
| 301 | * Can be called while holding spinlocks. |
| 302 | * |
| 303 | */ |
| 304 | static void get_futex_key_refs(union futex_key *key) |
| 305 | { |
| 306 | if (!key->both.ptr) |
| 307 | return; |
| 308 | |
| 309 | switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) { |
| 310 | case FUT_OFF_INODE: |
Davidlohr Bueso | b0c29f7 | 2014-01-12 15:31:25 -0800 | [diff] [blame] | 311 | ihold(key->shared.inode); /* implies MB (B) */ |
Peter Zijlstra | 38d47c1 | 2008-09-26 19:32:20 +0200 | [diff] [blame] | 312 | break; |
| 313 | case FUT_OFF_MMSHARED: |
Davidlohr Bueso | b0c29f7 | 2014-01-12 15:31:25 -0800 | [diff] [blame] | 314 | futex_get_mm(key); /* implies MB (B) */ |
Peter Zijlstra | 38d47c1 | 2008-09-26 19:32:20 +0200 | [diff] [blame] | 315 | break; |
| 316 | } |
| 317 | } |
| 318 | |
| 319 | /* |
| 320 | * Drop a reference to the resource addressed by a key. |
| 321 | * The hash bucket spinlock must not be held. |
| 322 | */ |
| 323 | static void drop_futex_key_refs(union futex_key *key) |
| 324 | { |
Darren Hart | 90621c4 | 2008-12-29 19:43:21 -0800 | [diff] [blame] | 325 | if (!key->both.ptr) { |
| 326 | /* If we're here then we tried to put a key we failed to get */ |
| 327 | WARN_ON_ONCE(1); |
Peter Zijlstra | 38d47c1 | 2008-09-26 19:32:20 +0200 | [diff] [blame] | 328 | return; |
Darren Hart | 90621c4 | 2008-12-29 19:43:21 -0800 | [diff] [blame] | 329 | } |
Peter Zijlstra | 38d47c1 | 2008-09-26 19:32:20 +0200 | [diff] [blame] | 330 | |
| 331 | switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) { |
| 332 | case FUT_OFF_INODE: |
| 333 | iput(key->shared.inode); |
| 334 | break; |
| 335 | case FUT_OFF_MMSHARED: |
| 336 | mmdrop(key->private.mm); |
| 337 | break; |
| 338 | } |
| 339 | } |
| 340 | |
Eric Dumazet | 34f01cc | 2007-05-09 02:35:04 -0700 | [diff] [blame] | 341 | /** |
Darren Hart | d96ee56 | 2009-09-21 22:30:22 -0700 | [diff] [blame] | 342 | * get_futex_key() - Get parameters which are the keys for a futex |
| 343 | * @uaddr: virtual address of the futex |
| 344 | * @fshared: 0 for a PROCESS_PRIVATE futex, 1 for PROCESS_SHARED |
| 345 | * @key: address where result is stored. |
Shawn Bohrer | 9ea7150 | 2011-06-30 11:21:32 -0500 | [diff] [blame] | 346 | * @rw: mapping needs to be read/write (values: VERIFY_READ, |
| 347 | * VERIFY_WRITE) |
Eric Dumazet | 34f01cc | 2007-05-09 02:35:04 -0700 | [diff] [blame] | 348 | * |
Randy Dunlap | 6c23cbb | 2013-03-05 10:00:24 -0800 | [diff] [blame] | 349 | * Return: a negative error code or 0 |
| 350 | * |
Eric Dumazet | 34f01cc | 2007-05-09 02:35:04 -0700 | [diff] [blame] | 351 | * The key words are stored in *key on success. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 352 | * |
Al Viro | 6131ffa | 2013-02-27 16:59:05 -0500 | [diff] [blame] | 353 | * For shared mappings, it's (page->index, file_inode(vma->vm_file), |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 354 | * offset_within_page). For private mappings, it's (uaddr, current->mm). |
| 355 | * We can usually work out the index without swapping in the page. |
| 356 | * |
Darren Hart | b2d0994 | 2009-03-12 00:55:37 -0700 | [diff] [blame] | 357 | * lock_page() might sleep, the caller should not hold a spinlock. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 358 | */ |
Thomas Gleixner | 64d1304 | 2009-05-18 21:20:10 +0200 | [diff] [blame] | 359 | static int |
Shawn Bohrer | 9ea7150 | 2011-06-30 11:21:32 -0500 | [diff] [blame] | 360 | get_futex_key(u32 __user *uaddr, int fshared, union futex_key *key, int rw) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 361 | { |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 362 | unsigned long address = (unsigned long)uaddr; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 363 | struct mm_struct *mm = current->mm; |
Andrea Arcangeli | a5b338f | 2011-01-13 15:46:34 -0800 | [diff] [blame] | 364 | struct page *page, *page_head; |
Shawn Bohrer | 9ea7150 | 2011-06-30 11:21:32 -0500 | [diff] [blame] | 365 | int err, ro = 0; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 366 | |
| 367 | /* |
| 368 | * The futex address must be "naturally" aligned. |
| 369 | */ |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 370 | key->both.offset = address % PAGE_SIZE; |
Eric Dumazet | 34f01cc | 2007-05-09 02:35:04 -0700 | [diff] [blame] | 371 | if (unlikely((address % sizeof(u32)) != 0)) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 372 | return -EINVAL; |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 373 | address -= key->both.offset; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 374 | |
Linus Torvalds | 5cdec2d | 2013-12-12 09:53:51 -0800 | [diff] [blame] | 375 | if (unlikely(!access_ok(rw, uaddr, sizeof(u32)))) |
| 376 | return -EFAULT; |
| 377 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 378 | /* |
Eric Dumazet | 34f01cc | 2007-05-09 02:35:04 -0700 | [diff] [blame] | 379 | * PROCESS_PRIVATE futexes are fast. |
| 380 | * As the mm cannot disappear under us and the 'key' only needs |
| 381 | * virtual address, we dont even have to find the underlying vma. |
| 382 | * Note : We do have to check 'uaddr' is a valid user address, |
| 383 | * but access_ok() should be faster than find_vma() |
| 384 | */ |
| 385 | if (!fshared) { |
Eric Dumazet | 34f01cc | 2007-05-09 02:35:04 -0700 | [diff] [blame] | 386 | key->private.mm = mm; |
| 387 | key->private.address = address; |
Davidlohr Bueso | b0c29f7 | 2014-01-12 15:31:25 -0800 | [diff] [blame] | 388 | get_futex_key_refs(key); /* implies MB (B) */ |
Eric Dumazet | 34f01cc | 2007-05-09 02:35:04 -0700 | [diff] [blame] | 389 | return 0; |
| 390 | } |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 391 | |
Peter Zijlstra | 38d47c1 | 2008-09-26 19:32:20 +0200 | [diff] [blame] | 392 | again: |
KOSAKI Motohiro | 7485d0d | 2010-01-05 16:32:43 +0900 | [diff] [blame] | 393 | err = get_user_pages_fast(address, 1, 1, &page); |
Shawn Bohrer | 9ea7150 | 2011-06-30 11:21:32 -0500 | [diff] [blame] | 394 | /* |
| 395 | * If write access is not required (eg. FUTEX_WAIT), try |
| 396 | * and get read-only access. |
| 397 | */ |
| 398 | if (err == -EFAULT && rw == VERIFY_READ) { |
| 399 | err = get_user_pages_fast(address, 1, 0, &page); |
| 400 | ro = 1; |
| 401 | } |
Peter Zijlstra | 38d47c1 | 2008-09-26 19:32:20 +0200 | [diff] [blame] | 402 | if (err < 0) |
| 403 | return err; |
Shawn Bohrer | 9ea7150 | 2011-06-30 11:21:32 -0500 | [diff] [blame] | 404 | else |
| 405 | err = 0; |
Peter Zijlstra | 38d47c1 | 2008-09-26 19:32:20 +0200 | [diff] [blame] | 406 | |
Andrea Arcangeli | a5b338f | 2011-01-13 15:46:34 -0800 | [diff] [blame] | 407 | #ifdef CONFIG_TRANSPARENT_HUGEPAGE |
| 408 | page_head = page; |
| 409 | if (unlikely(PageTail(page))) { |
Peter Zijlstra | 38d47c1 | 2008-09-26 19:32:20 +0200 | [diff] [blame] | 410 | put_page(page); |
Andrea Arcangeli | a5b338f | 2011-01-13 15:46:34 -0800 | [diff] [blame] | 411 | /* serialize against __split_huge_page_splitting() */ |
| 412 | local_irq_disable(); |
Linus Torvalds | f12d5bf | 2013-12-12 09:38:42 -0800 | [diff] [blame] | 413 | if (likely(__get_user_pages_fast(address, 1, !ro, &page) == 1)) { |
Andrea Arcangeli | a5b338f | 2011-01-13 15:46:34 -0800 | [diff] [blame] | 414 | page_head = compound_head(page); |
| 415 | /* |
| 416 | * page_head is valid pointer but we must pin |
| 417 | * it before taking the PG_lock and/or |
| 418 | * PG_compound_lock. The moment we re-enable |
| 419 | * irqs __split_huge_page_splitting() can |
| 420 | * return and the head page can be freed from |
| 421 | * under us. We can't take the PG_lock and/or |
| 422 | * PG_compound_lock on a page that could be |
| 423 | * freed from under us. |
| 424 | */ |
| 425 | if (page != page_head) { |
| 426 | get_page(page_head); |
| 427 | put_page(page); |
| 428 | } |
| 429 | local_irq_enable(); |
| 430 | } else { |
| 431 | local_irq_enable(); |
| 432 | goto again; |
| 433 | } |
| 434 | } |
| 435 | #else |
| 436 | page_head = compound_head(page); |
| 437 | if (page != page_head) { |
| 438 | get_page(page_head); |
| 439 | put_page(page); |
| 440 | } |
| 441 | #endif |
| 442 | |
| 443 | lock_page(page_head); |
Hugh Dickins | e6780f7 | 2011-12-31 11:44:01 -0800 | [diff] [blame] | 444 | |
| 445 | /* |
| 446 | * If page_head->mapping is NULL, then it cannot be a PageAnon |
| 447 | * page; but it might be the ZERO_PAGE or in the gate area or |
| 448 | * in a special mapping (all cases which we are happy to fail); |
| 449 | * or it may have been a good file page when get_user_pages_fast |
| 450 | * found it, but truncated or holepunched or subjected to |
| 451 | * invalidate_complete_page2 before we got the page lock (also |
| 452 | * cases which we are happy to fail). And we hold a reference, |
| 453 | * so refcount care in invalidate_complete_page's remove_mapping |
| 454 | * prevents drop_caches from setting mapping to NULL beneath us. |
| 455 | * |
| 456 | * The case we do have to guard against is when memory pressure made |
| 457 | * shmem_writepage move it from filecache to swapcache beneath us: |
| 458 | * an unlikely race, but we do need to retry for page_head->mapping. |
| 459 | */ |
Andrea Arcangeli | a5b338f | 2011-01-13 15:46:34 -0800 | [diff] [blame] | 460 | if (!page_head->mapping) { |
Hugh Dickins | e6780f7 | 2011-12-31 11:44:01 -0800 | [diff] [blame] | 461 | int shmem_swizzled = PageSwapCache(page_head); |
Andrea Arcangeli | a5b338f | 2011-01-13 15:46:34 -0800 | [diff] [blame] | 462 | unlock_page(page_head); |
| 463 | put_page(page_head); |
Hugh Dickins | e6780f7 | 2011-12-31 11:44:01 -0800 | [diff] [blame] | 464 | if (shmem_swizzled) |
| 465 | goto again; |
| 466 | return -EFAULT; |
Peter Zijlstra | 38d47c1 | 2008-09-26 19:32:20 +0200 | [diff] [blame] | 467 | } |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 468 | |
| 469 | /* |
| 470 | * Private mappings are handled in a simple way. |
| 471 | * |
| 472 | * NOTE: When userspace waits on a MAP_SHARED mapping, even if |
| 473 | * it's a read-only handle, it's expected that futexes attach to |
Peter Zijlstra | 38d47c1 | 2008-09-26 19:32:20 +0200 | [diff] [blame] | 474 | * the object not the particular process. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 475 | */ |
Andrea Arcangeli | a5b338f | 2011-01-13 15:46:34 -0800 | [diff] [blame] | 476 | if (PageAnon(page_head)) { |
Shawn Bohrer | 9ea7150 | 2011-06-30 11:21:32 -0500 | [diff] [blame] | 477 | /* |
| 478 | * A RO anonymous page will never change and thus doesn't make |
| 479 | * sense for futex operations. |
| 480 | */ |
| 481 | if (ro) { |
| 482 | err = -EFAULT; |
| 483 | goto out; |
| 484 | } |
| 485 | |
Peter Zijlstra | 38d47c1 | 2008-09-26 19:32:20 +0200 | [diff] [blame] | 486 | key->both.offset |= FUT_OFF_MMSHARED; /* ref taken on mm */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 487 | key->private.mm = mm; |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 488 | key->private.address = address; |
Peter Zijlstra | 38d47c1 | 2008-09-26 19:32:20 +0200 | [diff] [blame] | 489 | } else { |
| 490 | key->both.offset |= FUT_OFF_INODE; /* inode-based key */ |
Andrea Arcangeli | a5b338f | 2011-01-13 15:46:34 -0800 | [diff] [blame] | 491 | key->shared.inode = page_head->mapping->host; |
Zhang Yi | 13d60f4 | 2013-06-25 21:19:31 +0800 | [diff] [blame] | 492 | key->shared.pgoff = basepage_index(page); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 493 | } |
| 494 | |
Davidlohr Bueso | b0c29f7 | 2014-01-12 15:31:25 -0800 | [diff] [blame] | 495 | get_futex_key_refs(key); /* implies MB (B) */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 496 | |
Shawn Bohrer | 9ea7150 | 2011-06-30 11:21:32 -0500 | [diff] [blame] | 497 | out: |
Andrea Arcangeli | a5b338f | 2011-01-13 15:46:34 -0800 | [diff] [blame] | 498 | unlock_page(page_head); |
| 499 | put_page(page_head); |
Shawn Bohrer | 9ea7150 | 2011-06-30 11:21:32 -0500 | [diff] [blame] | 500 | return err; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 501 | } |
| 502 | |
Thomas Gleixner | ae791a2 | 2010-11-10 13:30:36 +0100 | [diff] [blame] | 503 | static inline void put_futex_key(union futex_key *key) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 504 | { |
Peter Zijlstra | 38d47c1 | 2008-09-26 19:32:20 +0200 | [diff] [blame] | 505 | drop_futex_key_refs(key); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 506 | } |
| 507 | |
Darren Hart | d96ee56 | 2009-09-21 22:30:22 -0700 | [diff] [blame] | 508 | /** |
| 509 | * fault_in_user_writeable() - Fault in user address and verify RW access |
Thomas Gleixner | d072599 | 2009-06-11 23:15:43 +0200 | [diff] [blame] | 510 | * @uaddr: pointer to faulting user space address |
| 511 | * |
| 512 | * Slow path to fixup the fault we just took in the atomic write |
| 513 | * access to @uaddr. |
| 514 | * |
Randy Dunlap | fb62db2 | 2010-10-13 11:02:34 -0700 | [diff] [blame] | 515 | * We have no generic implementation of a non-destructive write to the |
Thomas Gleixner | d072599 | 2009-06-11 23:15:43 +0200 | [diff] [blame] | 516 | * user address. We know that we faulted in the atomic pagefault |
| 517 | * disabled section so we can as well avoid the #PF overhead by |
| 518 | * calling get_user_pages() right away. |
| 519 | */ |
| 520 | static int fault_in_user_writeable(u32 __user *uaddr) |
| 521 | { |
Andi Kleen | 722d017 | 2009-12-08 13:19:42 +0100 | [diff] [blame] | 522 | struct mm_struct *mm = current->mm; |
| 523 | int ret; |
| 524 | |
| 525 | down_read(&mm->mmap_sem); |
Benjamin Herrenschmidt | 2efaca9 | 2011-07-25 17:12:32 -0700 | [diff] [blame] | 526 | ret = fixup_user_fault(current, mm, (unsigned long)uaddr, |
| 527 | FAULT_FLAG_WRITE); |
Andi Kleen | 722d017 | 2009-12-08 13:19:42 +0100 | [diff] [blame] | 528 | up_read(&mm->mmap_sem); |
| 529 | |
Thomas Gleixner | d072599 | 2009-06-11 23:15:43 +0200 | [diff] [blame] | 530 | return ret < 0 ? ret : 0; |
| 531 | } |
| 532 | |
Darren Hart | 4b1c486 | 2009-04-03 13:39:42 -0700 | [diff] [blame] | 533 | /** |
| 534 | * futex_top_waiter() - Return the highest priority waiter on a futex |
Darren Hart | d96ee56 | 2009-09-21 22:30:22 -0700 | [diff] [blame] | 535 | * @hb: the hash bucket the futex_q's reside in |
| 536 | * @key: the futex key (to distinguish it from other futex futex_q's) |
Darren Hart | 4b1c486 | 2009-04-03 13:39:42 -0700 | [diff] [blame] | 537 | * |
| 538 | * Must be called with the hb lock held. |
| 539 | */ |
| 540 | static struct futex_q *futex_top_waiter(struct futex_hash_bucket *hb, |
| 541 | union futex_key *key) |
| 542 | { |
| 543 | struct futex_q *this; |
| 544 | |
| 545 | plist_for_each_entry(this, &hb->chain, list) { |
| 546 | if (match_futex(&this->key, key)) |
| 547 | return this; |
| 548 | } |
| 549 | return NULL; |
| 550 | } |
| 551 | |
Michel Lespinasse | 37a9d91 | 2011-03-10 18:48:51 -0800 | [diff] [blame] | 552 | static int cmpxchg_futex_value_locked(u32 *curval, u32 __user *uaddr, |
| 553 | u32 uval, u32 newval) |
Thomas Gleixner | 36cf3b5 | 2007-07-15 23:41:20 -0700 | [diff] [blame] | 554 | { |
Michel Lespinasse | 37a9d91 | 2011-03-10 18:48:51 -0800 | [diff] [blame] | 555 | int ret; |
Thomas Gleixner | 36cf3b5 | 2007-07-15 23:41:20 -0700 | [diff] [blame] | 556 | |
| 557 | pagefault_disable(); |
Michel Lespinasse | 37a9d91 | 2011-03-10 18:48:51 -0800 | [diff] [blame] | 558 | ret = futex_atomic_cmpxchg_inatomic(curval, uaddr, uval, newval); |
Thomas Gleixner | 36cf3b5 | 2007-07-15 23:41:20 -0700 | [diff] [blame] | 559 | pagefault_enable(); |
| 560 | |
Michel Lespinasse | 37a9d91 | 2011-03-10 18:48:51 -0800 | [diff] [blame] | 561 | return ret; |
Thomas Gleixner | 36cf3b5 | 2007-07-15 23:41:20 -0700 | [diff] [blame] | 562 | } |
| 563 | |
| 564 | static int get_futex_value_locked(u32 *dest, u32 __user *from) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 565 | { |
| 566 | int ret; |
| 567 | |
Peter Zijlstra | a866374 | 2006-12-06 20:32:20 -0800 | [diff] [blame] | 568 | pagefault_disable(); |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 569 | ret = __copy_from_user_inatomic(dest, from, sizeof(u32)); |
Peter Zijlstra | a866374 | 2006-12-06 20:32:20 -0800 | [diff] [blame] | 570 | pagefault_enable(); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 571 | |
| 572 | return ret ? -EFAULT : 0; |
| 573 | } |
| 574 | |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 575 | |
| 576 | /* |
| 577 | * PI code: |
| 578 | */ |
| 579 | static int refill_pi_state_cache(void) |
| 580 | { |
| 581 | struct futex_pi_state *pi_state; |
| 582 | |
| 583 | if (likely(current->pi_state_cache)) |
| 584 | return 0; |
| 585 | |
Burman Yan | 4668edc | 2006-12-06 20:38:51 -0800 | [diff] [blame] | 586 | pi_state = kzalloc(sizeof(*pi_state), GFP_KERNEL); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 587 | |
| 588 | if (!pi_state) |
| 589 | return -ENOMEM; |
| 590 | |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 591 | INIT_LIST_HEAD(&pi_state->list); |
| 592 | /* pi_mutex gets initialized later */ |
| 593 | pi_state->owner = NULL; |
| 594 | atomic_set(&pi_state->refcount, 1); |
Peter Zijlstra | 38d47c1 | 2008-09-26 19:32:20 +0200 | [diff] [blame] | 595 | pi_state->key = FUTEX_KEY_INIT; |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 596 | |
| 597 | current->pi_state_cache = pi_state; |
| 598 | |
| 599 | return 0; |
| 600 | } |
| 601 | |
| 602 | static struct futex_pi_state * alloc_pi_state(void) |
| 603 | { |
| 604 | struct futex_pi_state *pi_state = current->pi_state_cache; |
| 605 | |
| 606 | WARN_ON(!pi_state); |
| 607 | current->pi_state_cache = NULL; |
| 608 | |
| 609 | return pi_state; |
| 610 | } |
| 611 | |
| 612 | static void free_pi_state(struct futex_pi_state *pi_state) |
| 613 | { |
| 614 | if (!atomic_dec_and_test(&pi_state->refcount)) |
| 615 | return; |
| 616 | |
| 617 | /* |
| 618 | * If pi_state->owner is NULL, the owner is most probably dying |
| 619 | * and has cleaned up the pi_state already |
| 620 | */ |
| 621 | if (pi_state->owner) { |
Thomas Gleixner | 1d61548 | 2009-11-17 14:54:03 +0100 | [diff] [blame] | 622 | raw_spin_lock_irq(&pi_state->owner->pi_lock); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 623 | list_del_init(&pi_state->list); |
Thomas Gleixner | 1d61548 | 2009-11-17 14:54:03 +0100 | [diff] [blame] | 624 | raw_spin_unlock_irq(&pi_state->owner->pi_lock); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 625 | |
| 626 | rt_mutex_proxy_unlock(&pi_state->pi_mutex, pi_state->owner); |
| 627 | } |
| 628 | |
| 629 | if (current->pi_state_cache) |
| 630 | kfree(pi_state); |
| 631 | else { |
| 632 | /* |
| 633 | * pi_state->list is already empty. |
| 634 | * clear pi_state->owner. |
| 635 | * refcount is at 0 - put it back to 1. |
| 636 | */ |
| 637 | pi_state->owner = NULL; |
| 638 | atomic_set(&pi_state->refcount, 1); |
| 639 | current->pi_state_cache = pi_state; |
| 640 | } |
| 641 | } |
| 642 | |
| 643 | /* |
| 644 | * Look up the task based on what TID userspace gave us. |
| 645 | * We dont trust it. |
| 646 | */ |
| 647 | static struct task_struct * futex_find_get_task(pid_t pid) |
| 648 | { |
| 649 | struct task_struct *p; |
| 650 | |
Oleg Nesterov | d359b54 | 2006-09-29 02:00:55 -0700 | [diff] [blame] | 651 | rcu_read_lock(); |
Pavel Emelyanov | 228ebcb | 2007-10-18 23:40:16 -0700 | [diff] [blame] | 652 | p = find_task_by_vpid(pid); |
Michal Hocko | 7a0ea09 | 2010-06-30 09:51:19 +0200 | [diff] [blame] | 653 | if (p) |
| 654 | get_task_struct(p); |
Thomas Gleixner | a06381f | 2007-06-23 11:48:40 +0200 | [diff] [blame] | 655 | |
Oleg Nesterov | d359b54 | 2006-09-29 02:00:55 -0700 | [diff] [blame] | 656 | rcu_read_unlock(); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 657 | |
| 658 | return p; |
| 659 | } |
| 660 | |
| 661 | /* |
| 662 | * This task is holding PI mutexes at exit time => bad. |
| 663 | * Kernel cleans up PI-state, but userspace is likely hosed. |
| 664 | * (Robust-futex cleanup is separate and might save the day for userspace.) |
| 665 | */ |
| 666 | void exit_pi_state_list(struct task_struct *curr) |
| 667 | { |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 668 | struct list_head *next, *head = &curr->pi_state_list; |
| 669 | struct futex_pi_state *pi_state; |
Ingo Molnar | 627371d | 2006-07-29 05:16:20 +0200 | [diff] [blame] | 670 | struct futex_hash_bucket *hb; |
Peter Zijlstra | 38d47c1 | 2008-09-26 19:32:20 +0200 | [diff] [blame] | 671 | union futex_key key = FUTEX_KEY_INIT; |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 672 | |
Thomas Gleixner | a0c1e90 | 2008-02-23 15:23:57 -0800 | [diff] [blame] | 673 | if (!futex_cmpxchg_enabled) |
| 674 | return; |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 675 | /* |
| 676 | * We are a ZOMBIE and nobody can enqueue itself on |
| 677 | * pi_state_list anymore, but we have to be careful |
Ingo Molnar | 627371d | 2006-07-29 05:16:20 +0200 | [diff] [blame] | 678 | * versus waiters unqueueing themselves: |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 679 | */ |
Thomas Gleixner | 1d61548 | 2009-11-17 14:54:03 +0100 | [diff] [blame] | 680 | raw_spin_lock_irq(&curr->pi_lock); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 681 | while (!list_empty(head)) { |
| 682 | |
| 683 | next = head->next; |
| 684 | pi_state = list_entry(next, struct futex_pi_state, list); |
| 685 | key = pi_state->key; |
Ingo Molnar | 627371d | 2006-07-29 05:16:20 +0200 | [diff] [blame] | 686 | hb = hash_futex(&key); |
Thomas Gleixner | 1d61548 | 2009-11-17 14:54:03 +0100 | [diff] [blame] | 687 | raw_spin_unlock_irq(&curr->pi_lock); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 688 | |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 689 | spin_lock(&hb->lock); |
| 690 | |
Thomas Gleixner | 1d61548 | 2009-11-17 14:54:03 +0100 | [diff] [blame] | 691 | raw_spin_lock_irq(&curr->pi_lock); |
Ingo Molnar | 627371d | 2006-07-29 05:16:20 +0200 | [diff] [blame] | 692 | /* |
| 693 | * We dropped the pi-lock, so re-check whether this |
| 694 | * task still owns the PI-state: |
| 695 | */ |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 696 | if (head->next != next) { |
| 697 | spin_unlock(&hb->lock); |
| 698 | continue; |
| 699 | } |
| 700 | |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 701 | WARN_ON(pi_state->owner != curr); |
Ingo Molnar | 627371d | 2006-07-29 05:16:20 +0200 | [diff] [blame] | 702 | WARN_ON(list_empty(&pi_state->list)); |
| 703 | list_del_init(&pi_state->list); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 704 | pi_state->owner = NULL; |
Thomas Gleixner | 1d61548 | 2009-11-17 14:54:03 +0100 | [diff] [blame] | 705 | raw_spin_unlock_irq(&curr->pi_lock); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 706 | |
| 707 | rt_mutex_unlock(&pi_state->pi_mutex); |
| 708 | |
| 709 | spin_unlock(&hb->lock); |
| 710 | |
Thomas Gleixner | 1d61548 | 2009-11-17 14:54:03 +0100 | [diff] [blame] | 711 | raw_spin_lock_irq(&curr->pi_lock); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 712 | } |
Thomas Gleixner | 1d61548 | 2009-11-17 14:54:03 +0100 | [diff] [blame] | 713 | raw_spin_unlock_irq(&curr->pi_lock); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 714 | } |
| 715 | |
| 716 | static int |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 717 | lookup_pi_state(u32 uval, struct futex_hash_bucket *hb, |
| 718 | union futex_key *key, struct futex_pi_state **ps) |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 719 | { |
| 720 | struct futex_pi_state *pi_state = NULL; |
| 721 | struct futex_q *this, *next; |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 722 | struct task_struct *p; |
Alexey Kuznetsov | 778e9a9 | 2007-06-08 13:47:00 -0700 | [diff] [blame] | 723 | pid_t pid = uval & FUTEX_TID_MASK; |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 724 | |
Jason Low | 0d00c7b | 2014-01-12 15:31:22 -0800 | [diff] [blame] | 725 | plist_for_each_entry_safe(this, next, &hb->chain, list) { |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 726 | if (match_futex(&this->key, key)) { |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 727 | /* |
| 728 | * Another waiter already exists - bump up |
| 729 | * the refcount and return its pi_state: |
| 730 | */ |
| 731 | pi_state = this->pi_state; |
Thomas Gleixner | 06a9ec2 | 2006-07-10 04:44:30 -0700 | [diff] [blame] | 732 | /* |
Randy Dunlap | fb62db2 | 2010-10-13 11:02:34 -0700 | [diff] [blame] | 733 | * Userspace might have messed up non-PI and PI futexes |
Thomas Gleixner | 06a9ec2 | 2006-07-10 04:44:30 -0700 | [diff] [blame] | 734 | */ |
| 735 | if (unlikely(!pi_state)) |
| 736 | return -EINVAL; |
| 737 | |
Ingo Molnar | 627371d | 2006-07-29 05:16:20 +0200 | [diff] [blame] | 738 | WARN_ON(!atomic_read(&pi_state->refcount)); |
Thomas Gleixner | 59647b6 | 2010-02-03 09:33:05 +0100 | [diff] [blame] | 739 | |
| 740 | /* |
| 741 | * When pi_state->owner is NULL then the owner died |
| 742 | * and another waiter is on the fly. pi_state->owner |
| 743 | * is fixed up by the task which acquires |
| 744 | * pi_state->rt_mutex. |
| 745 | * |
| 746 | * We do not check for pid == 0 which can happen when |
| 747 | * the owner died and robust_list_exit() cleared the |
| 748 | * TID. |
| 749 | */ |
| 750 | if (pid && pi_state->owner) { |
| 751 | /* |
| 752 | * Bail out if user space manipulated the |
| 753 | * futex value. |
| 754 | */ |
| 755 | if (pid != task_pid_vnr(pi_state->owner)) |
| 756 | return -EINVAL; |
| 757 | } |
Ingo Molnar | 627371d | 2006-07-29 05:16:20 +0200 | [diff] [blame] | 758 | |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 759 | atomic_inc(&pi_state->refcount); |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 760 | *ps = pi_state; |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 761 | |
| 762 | return 0; |
| 763 | } |
| 764 | } |
| 765 | |
| 766 | /* |
Ingo Molnar | e3f2dde | 2006-07-29 05:17:57 +0200 | [diff] [blame] | 767 | * We are the first waiter - try to look up the real owner and attach |
Alexey Kuznetsov | 778e9a9 | 2007-06-08 13:47:00 -0700 | [diff] [blame] | 768 | * the new pi_state to it, but bail out when TID = 0 |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 769 | */ |
Alexey Kuznetsov | 778e9a9 | 2007-06-08 13:47:00 -0700 | [diff] [blame] | 770 | if (!pid) |
Ingo Molnar | e3f2dde | 2006-07-29 05:17:57 +0200 | [diff] [blame] | 771 | return -ESRCH; |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 772 | p = futex_find_get_task(pid); |
Michal Hocko | 7a0ea09 | 2010-06-30 09:51:19 +0200 | [diff] [blame] | 773 | if (!p) |
| 774 | return -ESRCH; |
Alexey Kuznetsov | 778e9a9 | 2007-06-08 13:47:00 -0700 | [diff] [blame] | 775 | |
| 776 | /* |
| 777 | * We need to look at the task state flags to figure out, |
| 778 | * whether the task is exiting. To protect against the do_exit |
| 779 | * change of the task flags, we do this protected by |
| 780 | * p->pi_lock: |
| 781 | */ |
Thomas Gleixner | 1d61548 | 2009-11-17 14:54:03 +0100 | [diff] [blame] | 782 | raw_spin_lock_irq(&p->pi_lock); |
Alexey Kuznetsov | 778e9a9 | 2007-06-08 13:47:00 -0700 | [diff] [blame] | 783 | if (unlikely(p->flags & PF_EXITING)) { |
| 784 | /* |
| 785 | * The task is on the way out. When PF_EXITPIDONE is |
| 786 | * set, we know that the task has finished the |
| 787 | * cleanup: |
| 788 | */ |
| 789 | int ret = (p->flags & PF_EXITPIDONE) ? -ESRCH : -EAGAIN; |
| 790 | |
Thomas Gleixner | 1d61548 | 2009-11-17 14:54:03 +0100 | [diff] [blame] | 791 | raw_spin_unlock_irq(&p->pi_lock); |
Alexey Kuznetsov | 778e9a9 | 2007-06-08 13:47:00 -0700 | [diff] [blame] | 792 | put_task_struct(p); |
| 793 | return ret; |
| 794 | } |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 795 | |
| 796 | pi_state = alloc_pi_state(); |
| 797 | |
| 798 | /* |
| 799 | * Initialize the pi_mutex in locked state and make 'p' |
| 800 | * the owner of it: |
| 801 | */ |
| 802 | rt_mutex_init_proxy_locked(&pi_state->pi_mutex, p); |
| 803 | |
| 804 | /* Store the key for possible exit cleanups: */ |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 805 | pi_state->key = *key; |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 806 | |
Ingo Molnar | 627371d | 2006-07-29 05:16:20 +0200 | [diff] [blame] | 807 | WARN_ON(!list_empty(&pi_state->list)); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 808 | list_add(&pi_state->list, &p->pi_state_list); |
| 809 | pi_state->owner = p; |
Thomas Gleixner | 1d61548 | 2009-11-17 14:54:03 +0100 | [diff] [blame] | 810 | raw_spin_unlock_irq(&p->pi_lock); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 811 | |
| 812 | put_task_struct(p); |
| 813 | |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 814 | *ps = pi_state; |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 815 | |
| 816 | return 0; |
| 817 | } |
| 818 | |
Darren Hart | 1a52084 | 2009-04-03 13:39:52 -0700 | [diff] [blame] | 819 | /** |
Darren Hart | d96ee56 | 2009-09-21 22:30:22 -0700 | [diff] [blame] | 820 | * futex_lock_pi_atomic() - Atomic work required to acquire a pi aware futex |
Darren Hart | bab5bc9 | 2009-04-07 23:23:50 -0700 | [diff] [blame] | 821 | * @uaddr: the pi futex user address |
| 822 | * @hb: the pi futex hash bucket |
| 823 | * @key: the futex key associated with uaddr and hb |
| 824 | * @ps: the pi_state pointer where we store the result of the |
| 825 | * lookup |
| 826 | * @task: the task to perform the atomic lock work for. This will |
| 827 | * be "current" except in the case of requeue pi. |
| 828 | * @set_waiters: force setting the FUTEX_WAITERS bit (1) or not (0) |
Darren Hart | 1a52084 | 2009-04-03 13:39:52 -0700 | [diff] [blame] | 829 | * |
Randy Dunlap | 6c23cbb | 2013-03-05 10:00:24 -0800 | [diff] [blame] | 830 | * Return: |
| 831 | * 0 - ready to wait; |
| 832 | * 1 - acquired the lock; |
Darren Hart | 1a52084 | 2009-04-03 13:39:52 -0700 | [diff] [blame] | 833 | * <0 - error |
| 834 | * |
| 835 | * The hb->lock and futex_key refs shall be held by the caller. |
| 836 | */ |
| 837 | static int futex_lock_pi_atomic(u32 __user *uaddr, struct futex_hash_bucket *hb, |
| 838 | union futex_key *key, |
| 839 | struct futex_pi_state **ps, |
Darren Hart | bab5bc9 | 2009-04-07 23:23:50 -0700 | [diff] [blame] | 840 | struct task_struct *task, int set_waiters) |
Darren Hart | 1a52084 | 2009-04-03 13:39:52 -0700 | [diff] [blame] | 841 | { |
Thomas Gleixner | 59fa624 | 2012-10-23 22:29:38 +0200 | [diff] [blame] | 842 | int lock_taken, ret, force_take = 0; |
Thomas Gleixner | c0c9ed1 | 2011-03-11 11:51:22 +0100 | [diff] [blame] | 843 | u32 uval, newval, curval, vpid = task_pid_vnr(task); |
Darren Hart | 1a52084 | 2009-04-03 13:39:52 -0700 | [diff] [blame] | 844 | |
| 845 | retry: |
| 846 | ret = lock_taken = 0; |
| 847 | |
| 848 | /* |
| 849 | * To avoid races, we attempt to take the lock here again |
| 850 | * (by doing a 0 -> TID atomic cmpxchg), while holding all |
| 851 | * the locks. It will most likely not succeed. |
| 852 | */ |
Thomas Gleixner | c0c9ed1 | 2011-03-11 11:51:22 +0100 | [diff] [blame] | 853 | newval = vpid; |
Darren Hart | bab5bc9 | 2009-04-07 23:23:50 -0700 | [diff] [blame] | 854 | if (set_waiters) |
| 855 | newval |= FUTEX_WAITERS; |
Darren Hart | 1a52084 | 2009-04-03 13:39:52 -0700 | [diff] [blame] | 856 | |
Michel Lespinasse | 37a9d91 | 2011-03-10 18:48:51 -0800 | [diff] [blame] | 857 | if (unlikely(cmpxchg_futex_value_locked(&curval, uaddr, 0, newval))) |
Darren Hart | 1a52084 | 2009-04-03 13:39:52 -0700 | [diff] [blame] | 858 | return -EFAULT; |
| 859 | |
| 860 | /* |
| 861 | * Detect deadlocks. |
| 862 | */ |
Thomas Gleixner | c0c9ed1 | 2011-03-11 11:51:22 +0100 | [diff] [blame] | 863 | if ((unlikely((curval & FUTEX_TID_MASK) == vpid))) |
Darren Hart | 1a52084 | 2009-04-03 13:39:52 -0700 | [diff] [blame] | 864 | return -EDEADLK; |
| 865 | |
| 866 | /* |
| 867 | * Surprise - we got the lock. Just return to userspace: |
| 868 | */ |
| 869 | if (unlikely(!curval)) |
| 870 | return 1; |
| 871 | |
| 872 | uval = curval; |
| 873 | |
| 874 | /* |
| 875 | * Set the FUTEX_WAITERS flag, so the owner will know it has someone |
| 876 | * to wake at the next unlock. |
| 877 | */ |
| 878 | newval = curval | FUTEX_WAITERS; |
| 879 | |
| 880 | /* |
Thomas Gleixner | 59fa624 | 2012-10-23 22:29:38 +0200 | [diff] [blame] | 881 | * Should we force take the futex? See below. |
Darren Hart | 1a52084 | 2009-04-03 13:39:52 -0700 | [diff] [blame] | 882 | */ |
Thomas Gleixner | 59fa624 | 2012-10-23 22:29:38 +0200 | [diff] [blame] | 883 | if (unlikely(force_take)) { |
| 884 | /* |
| 885 | * Keep the OWNER_DIED and the WAITERS bit and set the |
| 886 | * new TID value. |
| 887 | */ |
Thomas Gleixner | c0c9ed1 | 2011-03-11 11:51:22 +0100 | [diff] [blame] | 888 | newval = (curval & ~FUTEX_TID_MASK) | vpid; |
Thomas Gleixner | 59fa624 | 2012-10-23 22:29:38 +0200 | [diff] [blame] | 889 | force_take = 0; |
Darren Hart | 1a52084 | 2009-04-03 13:39:52 -0700 | [diff] [blame] | 890 | lock_taken = 1; |
| 891 | } |
| 892 | |
Michel Lespinasse | 37a9d91 | 2011-03-10 18:48:51 -0800 | [diff] [blame] | 893 | if (unlikely(cmpxchg_futex_value_locked(&curval, uaddr, uval, newval))) |
Darren Hart | 1a52084 | 2009-04-03 13:39:52 -0700 | [diff] [blame] | 894 | return -EFAULT; |
| 895 | if (unlikely(curval != uval)) |
| 896 | goto retry; |
| 897 | |
| 898 | /* |
Thomas Gleixner | 59fa624 | 2012-10-23 22:29:38 +0200 | [diff] [blame] | 899 | * We took the lock due to forced take over. |
Darren Hart | 1a52084 | 2009-04-03 13:39:52 -0700 | [diff] [blame] | 900 | */ |
| 901 | if (unlikely(lock_taken)) |
| 902 | return 1; |
| 903 | |
| 904 | /* |
| 905 | * We dont have the lock. Look up the PI state (or create it if |
| 906 | * we are the first waiter): |
| 907 | */ |
| 908 | ret = lookup_pi_state(uval, hb, key, ps); |
| 909 | |
| 910 | if (unlikely(ret)) { |
| 911 | switch (ret) { |
| 912 | case -ESRCH: |
| 913 | /* |
Thomas Gleixner | 59fa624 | 2012-10-23 22:29:38 +0200 | [diff] [blame] | 914 | * We failed to find an owner for this |
| 915 | * futex. So we have no pi_state to block |
| 916 | * on. This can happen in two cases: |
| 917 | * |
| 918 | * 1) The owner died |
| 919 | * 2) A stale FUTEX_WAITERS bit |
| 920 | * |
| 921 | * Re-read the futex value. |
Darren Hart | 1a52084 | 2009-04-03 13:39:52 -0700 | [diff] [blame] | 922 | */ |
| 923 | if (get_futex_value_locked(&curval, uaddr)) |
| 924 | return -EFAULT; |
| 925 | |
| 926 | /* |
Thomas Gleixner | 59fa624 | 2012-10-23 22:29:38 +0200 | [diff] [blame] | 927 | * If the owner died or we have a stale |
| 928 | * WAITERS bit the owner TID in the user space |
| 929 | * futex is 0. |
Darren Hart | 1a52084 | 2009-04-03 13:39:52 -0700 | [diff] [blame] | 930 | */ |
Thomas Gleixner | 59fa624 | 2012-10-23 22:29:38 +0200 | [diff] [blame] | 931 | if (!(curval & FUTEX_TID_MASK)) { |
| 932 | force_take = 1; |
Darren Hart | 1a52084 | 2009-04-03 13:39:52 -0700 | [diff] [blame] | 933 | goto retry; |
| 934 | } |
| 935 | default: |
| 936 | break; |
| 937 | } |
| 938 | } |
| 939 | |
| 940 | return ret; |
| 941 | } |
| 942 | |
Lai Jiangshan | 2e12978 | 2010-12-22 14:18:50 +0800 | [diff] [blame] | 943 | /** |
| 944 | * __unqueue_futex() - Remove the futex_q from its futex_hash_bucket |
| 945 | * @q: The futex_q to unqueue |
| 946 | * |
| 947 | * The q->lock_ptr must not be NULL and must be held by the caller. |
| 948 | */ |
| 949 | static void __unqueue_futex(struct futex_q *q) |
| 950 | { |
| 951 | struct futex_hash_bucket *hb; |
| 952 | |
Steven Rostedt | 2909620 | 2011-03-17 15:21:07 -0400 | [diff] [blame] | 953 | if (WARN_ON_SMP(!q->lock_ptr || !spin_is_locked(q->lock_ptr)) |
| 954 | || WARN_ON(plist_node_empty(&q->list))) |
Lai Jiangshan | 2e12978 | 2010-12-22 14:18:50 +0800 | [diff] [blame] | 955 | return; |
| 956 | |
| 957 | hb = container_of(q->lock_ptr, struct futex_hash_bucket, lock); |
| 958 | plist_del(&q->list, &hb->chain); |
| 959 | } |
| 960 | |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 961 | /* |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 962 | * The hash bucket lock must be held when this is called. |
| 963 | * Afterwards, the futex_q must not be accessed. |
| 964 | */ |
| 965 | static void wake_futex(struct futex_q *q) |
| 966 | { |
Thomas Gleixner | f1a11e0 | 2009-05-05 19:21:40 +0200 | [diff] [blame] | 967 | struct task_struct *p = q->task; |
| 968 | |
Darren Hart | aa10990 | 2012-11-26 16:29:56 -0800 | [diff] [blame] | 969 | if (WARN(q->pi_state || q->rt_waiter, "refusing to wake PI futex\n")) |
| 970 | return; |
| 971 | |
Thomas Gleixner | f1a11e0 | 2009-05-05 19:21:40 +0200 | [diff] [blame] | 972 | /* |
| 973 | * We set q->lock_ptr = NULL _before_ we wake up the task. If |
Randy Dunlap | fb62db2 | 2010-10-13 11:02:34 -0700 | [diff] [blame] | 974 | * a non-futex wake up happens on another CPU then the task |
| 975 | * might exit and p would dereference a non-existing task |
Thomas Gleixner | f1a11e0 | 2009-05-05 19:21:40 +0200 | [diff] [blame] | 976 | * struct. Prevent this by holding a reference on p across the |
| 977 | * wake up. |
| 978 | */ |
| 979 | get_task_struct(p); |
| 980 | |
Lai Jiangshan | 2e12978 | 2010-12-22 14:18:50 +0800 | [diff] [blame] | 981 | __unqueue_futex(q); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 982 | /* |
Thomas Gleixner | f1a11e0 | 2009-05-05 19:21:40 +0200 | [diff] [blame] | 983 | * The waiting task can free the futex_q as soon as |
| 984 | * q->lock_ptr = NULL is written, without taking any locks. A |
| 985 | * memory barrier is required here to prevent the following |
| 986 | * store to lock_ptr from getting ahead of the plist_del. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 987 | */ |
Ralf Baechle | ccdea2f | 2006-12-06 20:40:26 -0800 | [diff] [blame] | 988 | smp_wmb(); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 989 | q->lock_ptr = NULL; |
Thomas Gleixner | f1a11e0 | 2009-05-05 19:21:40 +0200 | [diff] [blame] | 990 | |
| 991 | wake_up_state(p, TASK_NORMAL); |
| 992 | put_task_struct(p); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 993 | } |
| 994 | |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 995 | static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this) |
| 996 | { |
| 997 | struct task_struct *new_owner; |
| 998 | struct futex_pi_state *pi_state = this->pi_state; |
Vitaliy Ivanov | 7cfdaf3 | 2011-07-07 15:10:31 +0300 | [diff] [blame] | 999 | u32 uninitialized_var(curval), newval; |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1000 | |
| 1001 | if (!pi_state) |
| 1002 | return -EINVAL; |
| 1003 | |
Thomas Gleixner | 51246bf | 2010-02-02 11:40:27 +0100 | [diff] [blame] | 1004 | /* |
| 1005 | * If current does not own the pi_state then the futex is |
| 1006 | * inconsistent and user space fiddled with the futex value. |
| 1007 | */ |
| 1008 | if (pi_state->owner != current) |
| 1009 | return -EINVAL; |
| 1010 | |
Thomas Gleixner | d209d74 | 2009-11-17 18:22:11 +0100 | [diff] [blame] | 1011 | raw_spin_lock(&pi_state->pi_mutex.wait_lock); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1012 | new_owner = rt_mutex_next_owner(&pi_state->pi_mutex); |
| 1013 | |
| 1014 | /* |
Steven Rostedt | f123c98 | 2011-01-06 15:08:29 -0500 | [diff] [blame] | 1015 | * It is possible that the next waiter (the one that brought |
| 1016 | * this owner to the kernel) timed out and is no longer |
| 1017 | * waiting on the lock. |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1018 | */ |
| 1019 | if (!new_owner) |
| 1020 | new_owner = this->task; |
| 1021 | |
| 1022 | /* |
| 1023 | * We pass it to the next owner. (The WAITERS bit is always |
| 1024 | * kept enabled while there is PI state around. We must also |
| 1025 | * preserve the owner died bit.) |
| 1026 | */ |
Ingo Molnar | e3f2dde | 2006-07-29 05:17:57 +0200 | [diff] [blame] | 1027 | if (!(uval & FUTEX_OWNER_DIED)) { |
Alexey Kuznetsov | 778e9a9 | 2007-06-08 13:47:00 -0700 | [diff] [blame] | 1028 | int ret = 0; |
| 1029 | |
Pavel Emelyanov | b488893 | 2007-10-18 23:40:14 -0700 | [diff] [blame] | 1030 | newval = FUTEX_WAITERS | task_pid_vnr(new_owner); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1031 | |
Michel Lespinasse | 37a9d91 | 2011-03-10 18:48:51 -0800 | [diff] [blame] | 1032 | if (cmpxchg_futex_value_locked(&curval, uaddr, uval, newval)) |
Alexey Kuznetsov | 778e9a9 | 2007-06-08 13:47:00 -0700 | [diff] [blame] | 1033 | ret = -EFAULT; |
Thomas Gleixner | cde898f | 2007-12-05 15:46:09 +0100 | [diff] [blame] | 1034 | else if (curval != uval) |
Alexey Kuznetsov | 778e9a9 | 2007-06-08 13:47:00 -0700 | [diff] [blame] | 1035 | ret = -EINVAL; |
| 1036 | if (ret) { |
Thomas Gleixner | d209d74 | 2009-11-17 18:22:11 +0100 | [diff] [blame] | 1037 | raw_spin_unlock(&pi_state->pi_mutex.wait_lock); |
Alexey Kuznetsov | 778e9a9 | 2007-06-08 13:47:00 -0700 | [diff] [blame] | 1038 | return ret; |
| 1039 | } |
Ingo Molnar | e3f2dde | 2006-07-29 05:17:57 +0200 | [diff] [blame] | 1040 | } |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1041 | |
Thomas Gleixner | 1d61548 | 2009-11-17 14:54:03 +0100 | [diff] [blame] | 1042 | raw_spin_lock_irq(&pi_state->owner->pi_lock); |
Ingo Molnar | 627371d | 2006-07-29 05:16:20 +0200 | [diff] [blame] | 1043 | WARN_ON(list_empty(&pi_state->list)); |
| 1044 | list_del_init(&pi_state->list); |
Thomas Gleixner | 1d61548 | 2009-11-17 14:54:03 +0100 | [diff] [blame] | 1045 | raw_spin_unlock_irq(&pi_state->owner->pi_lock); |
Ingo Molnar | 627371d | 2006-07-29 05:16:20 +0200 | [diff] [blame] | 1046 | |
Thomas Gleixner | 1d61548 | 2009-11-17 14:54:03 +0100 | [diff] [blame] | 1047 | raw_spin_lock_irq(&new_owner->pi_lock); |
Ingo Molnar | 627371d | 2006-07-29 05:16:20 +0200 | [diff] [blame] | 1048 | WARN_ON(!list_empty(&pi_state->list)); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1049 | list_add(&pi_state->list, &new_owner->pi_state_list); |
| 1050 | pi_state->owner = new_owner; |
Thomas Gleixner | 1d61548 | 2009-11-17 14:54:03 +0100 | [diff] [blame] | 1051 | raw_spin_unlock_irq(&new_owner->pi_lock); |
Ingo Molnar | 627371d | 2006-07-29 05:16:20 +0200 | [diff] [blame] | 1052 | |
Thomas Gleixner | d209d74 | 2009-11-17 18:22:11 +0100 | [diff] [blame] | 1053 | raw_spin_unlock(&pi_state->pi_mutex.wait_lock); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1054 | rt_mutex_unlock(&pi_state->pi_mutex); |
| 1055 | |
| 1056 | return 0; |
| 1057 | } |
| 1058 | |
| 1059 | static int unlock_futex_pi(u32 __user *uaddr, u32 uval) |
| 1060 | { |
Vitaliy Ivanov | 7cfdaf3 | 2011-07-07 15:10:31 +0300 | [diff] [blame] | 1061 | u32 uninitialized_var(oldval); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1062 | |
| 1063 | /* |
| 1064 | * There is no waiter, so we unlock the futex. The owner died |
| 1065 | * bit has not to be preserved here. We are the owner: |
| 1066 | */ |
Michel Lespinasse | 37a9d91 | 2011-03-10 18:48:51 -0800 | [diff] [blame] | 1067 | if (cmpxchg_futex_value_locked(&oldval, uaddr, uval, 0)) |
| 1068 | return -EFAULT; |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1069 | if (oldval != uval) |
| 1070 | return -EAGAIN; |
| 1071 | |
| 1072 | return 0; |
| 1073 | } |
| 1074 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1075 | /* |
Ingo Molnar | 8b8f319 | 2006-07-03 00:25:05 -0700 | [diff] [blame] | 1076 | * Express the locking dependencies for lockdep: |
| 1077 | */ |
| 1078 | static inline void |
| 1079 | double_lock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2) |
| 1080 | { |
| 1081 | if (hb1 <= hb2) { |
| 1082 | spin_lock(&hb1->lock); |
| 1083 | if (hb1 < hb2) |
| 1084 | spin_lock_nested(&hb2->lock, SINGLE_DEPTH_NESTING); |
| 1085 | } else { /* hb1 > hb2 */ |
| 1086 | spin_lock(&hb2->lock); |
| 1087 | spin_lock_nested(&hb1->lock, SINGLE_DEPTH_NESTING); |
| 1088 | } |
| 1089 | } |
| 1090 | |
Darren Hart | 5eb3dc6 | 2009-03-12 00:55:52 -0700 | [diff] [blame] | 1091 | static inline void |
| 1092 | double_unlock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2) |
| 1093 | { |
Darren Hart | f061d35 | 2009-03-12 15:11:18 -0700 | [diff] [blame] | 1094 | spin_unlock(&hb1->lock); |
Ingo Molnar | 88f502f | 2009-03-13 10:32:07 +0100 | [diff] [blame] | 1095 | if (hb1 != hb2) |
| 1096 | spin_unlock(&hb2->lock); |
Darren Hart | 5eb3dc6 | 2009-03-12 00:55:52 -0700 | [diff] [blame] | 1097 | } |
| 1098 | |
Ingo Molnar | 8b8f319 | 2006-07-03 00:25:05 -0700 | [diff] [blame] | 1099 | /* |
Darren Hart | b2d0994 | 2009-03-12 00:55:37 -0700 | [diff] [blame] | 1100 | * Wake up waiters matching bitset queued on this futex (uaddr). |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1101 | */ |
Darren Hart | b41277d | 2010-11-08 13:10:09 -0800 | [diff] [blame] | 1102 | static int |
| 1103 | futex_wake(u32 __user *uaddr, unsigned int flags, int nr_wake, u32 bitset) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1104 | { |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 1105 | struct futex_hash_bucket *hb; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1106 | struct futex_q *this, *next; |
Peter Zijlstra | 38d47c1 | 2008-09-26 19:32:20 +0200 | [diff] [blame] | 1107 | union futex_key key = FUTEX_KEY_INIT; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1108 | int ret; |
| 1109 | |
Thomas Gleixner | cd68998 | 2008-02-01 17:45:14 +0100 | [diff] [blame] | 1110 | if (!bitset) |
| 1111 | return -EINVAL; |
| 1112 | |
Shawn Bohrer | 9ea7150 | 2011-06-30 11:21:32 -0500 | [diff] [blame] | 1113 | ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &key, VERIFY_READ); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1114 | if (unlikely(ret != 0)) |
| 1115 | goto out; |
| 1116 | |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 1117 | hb = hash_futex(&key); |
Davidlohr Bueso | b0c29f7 | 2014-01-12 15:31:25 -0800 | [diff] [blame] | 1118 | |
| 1119 | /* Make sure we really have tasks to wakeup */ |
| 1120 | if (!hb_waiters_pending(hb)) |
| 1121 | goto out_put_key; |
| 1122 | |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 1123 | spin_lock(&hb->lock); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1124 | |
Jason Low | 0d00c7b | 2014-01-12 15:31:22 -0800 | [diff] [blame] | 1125 | plist_for_each_entry_safe(this, next, &hb->chain, list) { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1126 | if (match_futex (&this->key, &key)) { |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1127 | if (this->pi_state || this->rt_waiter) { |
Ingo Molnar | ed6f7b1 | 2006-07-01 04:35:46 -0700 | [diff] [blame] | 1128 | ret = -EINVAL; |
| 1129 | break; |
| 1130 | } |
Thomas Gleixner | cd68998 | 2008-02-01 17:45:14 +0100 | [diff] [blame] | 1131 | |
| 1132 | /* Check if one of the bits is set in both bitsets */ |
| 1133 | if (!(this->bitset & bitset)) |
| 1134 | continue; |
| 1135 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1136 | wake_futex(this); |
| 1137 | if (++ret >= nr_wake) |
| 1138 | break; |
| 1139 | } |
| 1140 | } |
| 1141 | |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 1142 | spin_unlock(&hb->lock); |
Davidlohr Bueso | b0c29f7 | 2014-01-12 15:31:25 -0800 | [diff] [blame] | 1143 | out_put_key: |
Thomas Gleixner | ae791a2 | 2010-11-10 13:30:36 +0100 | [diff] [blame] | 1144 | put_futex_key(&key); |
Darren Hart | 42d35d4 | 2008-12-29 15:49:53 -0800 | [diff] [blame] | 1145 | out: |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1146 | return ret; |
| 1147 | } |
| 1148 | |
| 1149 | /* |
Jakub Jelinek | 4732efb | 2005-09-06 15:16:25 -0700 | [diff] [blame] | 1150 | * Wake up all waiters hashed on the physical page that is mapped |
| 1151 | * to this virtual address: |
| 1152 | */ |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 1153 | static int |
Darren Hart | b41277d | 2010-11-08 13:10:09 -0800 | [diff] [blame] | 1154 | futex_wake_op(u32 __user *uaddr1, unsigned int flags, u32 __user *uaddr2, |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 1155 | int nr_wake, int nr_wake2, int op) |
Jakub Jelinek | 4732efb | 2005-09-06 15:16:25 -0700 | [diff] [blame] | 1156 | { |
Peter Zijlstra | 38d47c1 | 2008-09-26 19:32:20 +0200 | [diff] [blame] | 1157 | union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT; |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 1158 | struct futex_hash_bucket *hb1, *hb2; |
Jakub Jelinek | 4732efb | 2005-09-06 15:16:25 -0700 | [diff] [blame] | 1159 | struct futex_q *this, *next; |
Darren Hart | e4dc5b7 | 2009-03-12 00:56:13 -0700 | [diff] [blame] | 1160 | int ret, op_ret; |
Jakub Jelinek | 4732efb | 2005-09-06 15:16:25 -0700 | [diff] [blame] | 1161 | |
Darren Hart | e4dc5b7 | 2009-03-12 00:56:13 -0700 | [diff] [blame] | 1162 | retry: |
Shawn Bohrer | 9ea7150 | 2011-06-30 11:21:32 -0500 | [diff] [blame] | 1163 | ret = get_futex_key(uaddr1, flags & FLAGS_SHARED, &key1, VERIFY_READ); |
Jakub Jelinek | 4732efb | 2005-09-06 15:16:25 -0700 | [diff] [blame] | 1164 | if (unlikely(ret != 0)) |
| 1165 | goto out; |
Shawn Bohrer | 9ea7150 | 2011-06-30 11:21:32 -0500 | [diff] [blame] | 1166 | ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2, VERIFY_WRITE); |
Jakub Jelinek | 4732efb | 2005-09-06 15:16:25 -0700 | [diff] [blame] | 1167 | if (unlikely(ret != 0)) |
Darren Hart | 42d35d4 | 2008-12-29 15:49:53 -0800 | [diff] [blame] | 1168 | goto out_put_key1; |
Jakub Jelinek | 4732efb | 2005-09-06 15:16:25 -0700 | [diff] [blame] | 1169 | |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 1170 | hb1 = hash_futex(&key1); |
| 1171 | hb2 = hash_futex(&key2); |
Jakub Jelinek | 4732efb | 2005-09-06 15:16:25 -0700 | [diff] [blame] | 1172 | |
Darren Hart | e4dc5b7 | 2009-03-12 00:56:13 -0700 | [diff] [blame] | 1173 | retry_private: |
Thomas Gleixner | eaaea80 | 2009-10-04 09:34:17 +0200 | [diff] [blame] | 1174 | double_lock_hb(hb1, hb2); |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 1175 | op_ret = futex_atomic_op_inuser(op, uaddr2); |
Jakub Jelinek | 4732efb | 2005-09-06 15:16:25 -0700 | [diff] [blame] | 1176 | if (unlikely(op_ret < 0)) { |
Jakub Jelinek | 4732efb | 2005-09-06 15:16:25 -0700 | [diff] [blame] | 1177 | |
Darren Hart | 5eb3dc6 | 2009-03-12 00:55:52 -0700 | [diff] [blame] | 1178 | double_unlock_hb(hb1, hb2); |
Jakub Jelinek | 4732efb | 2005-09-06 15:16:25 -0700 | [diff] [blame] | 1179 | |
David Howells | 7ee1dd3 | 2006-01-06 00:11:44 -0800 | [diff] [blame] | 1180 | #ifndef CONFIG_MMU |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 1181 | /* |
| 1182 | * we don't get EFAULT from MMU faults if we don't have an MMU, |
| 1183 | * but we might get them from range checking |
| 1184 | */ |
David Howells | 7ee1dd3 | 2006-01-06 00:11:44 -0800 | [diff] [blame] | 1185 | ret = op_ret; |
Darren Hart | 42d35d4 | 2008-12-29 15:49:53 -0800 | [diff] [blame] | 1186 | goto out_put_keys; |
David Howells | 7ee1dd3 | 2006-01-06 00:11:44 -0800 | [diff] [blame] | 1187 | #endif |
| 1188 | |
David Gibson | 796f8d9 | 2005-11-07 00:59:33 -0800 | [diff] [blame] | 1189 | if (unlikely(op_ret != -EFAULT)) { |
| 1190 | ret = op_ret; |
Darren Hart | 42d35d4 | 2008-12-29 15:49:53 -0800 | [diff] [blame] | 1191 | goto out_put_keys; |
David Gibson | 796f8d9 | 2005-11-07 00:59:33 -0800 | [diff] [blame] | 1192 | } |
| 1193 | |
Thomas Gleixner | d072599 | 2009-06-11 23:15:43 +0200 | [diff] [blame] | 1194 | ret = fault_in_user_writeable(uaddr2); |
Jakub Jelinek | 4732efb | 2005-09-06 15:16:25 -0700 | [diff] [blame] | 1195 | if (ret) |
Darren Hart | de87fcc | 2009-03-12 00:55:46 -0700 | [diff] [blame] | 1196 | goto out_put_keys; |
Jakub Jelinek | 4732efb | 2005-09-06 15:16:25 -0700 | [diff] [blame] | 1197 | |
Darren Hart | b41277d | 2010-11-08 13:10:09 -0800 | [diff] [blame] | 1198 | if (!(flags & FLAGS_SHARED)) |
Darren Hart | e4dc5b7 | 2009-03-12 00:56:13 -0700 | [diff] [blame] | 1199 | goto retry_private; |
| 1200 | |
Thomas Gleixner | ae791a2 | 2010-11-10 13:30:36 +0100 | [diff] [blame] | 1201 | put_futex_key(&key2); |
| 1202 | put_futex_key(&key1); |
Darren Hart | e4dc5b7 | 2009-03-12 00:56:13 -0700 | [diff] [blame] | 1203 | goto retry; |
Jakub Jelinek | 4732efb | 2005-09-06 15:16:25 -0700 | [diff] [blame] | 1204 | } |
| 1205 | |
Jason Low | 0d00c7b | 2014-01-12 15:31:22 -0800 | [diff] [blame] | 1206 | plist_for_each_entry_safe(this, next, &hb1->chain, list) { |
Jakub Jelinek | 4732efb | 2005-09-06 15:16:25 -0700 | [diff] [blame] | 1207 | if (match_futex (&this->key, &key1)) { |
Darren Hart | aa10990 | 2012-11-26 16:29:56 -0800 | [diff] [blame] | 1208 | if (this->pi_state || this->rt_waiter) { |
| 1209 | ret = -EINVAL; |
| 1210 | goto out_unlock; |
| 1211 | } |
Jakub Jelinek | 4732efb | 2005-09-06 15:16:25 -0700 | [diff] [blame] | 1212 | wake_futex(this); |
| 1213 | if (++ret >= nr_wake) |
| 1214 | break; |
| 1215 | } |
| 1216 | } |
| 1217 | |
| 1218 | if (op_ret > 0) { |
Jakub Jelinek | 4732efb | 2005-09-06 15:16:25 -0700 | [diff] [blame] | 1219 | op_ret = 0; |
Jason Low | 0d00c7b | 2014-01-12 15:31:22 -0800 | [diff] [blame] | 1220 | plist_for_each_entry_safe(this, next, &hb2->chain, list) { |
Jakub Jelinek | 4732efb | 2005-09-06 15:16:25 -0700 | [diff] [blame] | 1221 | if (match_futex (&this->key, &key2)) { |
Darren Hart | aa10990 | 2012-11-26 16:29:56 -0800 | [diff] [blame] | 1222 | if (this->pi_state || this->rt_waiter) { |
| 1223 | ret = -EINVAL; |
| 1224 | goto out_unlock; |
| 1225 | } |
Jakub Jelinek | 4732efb | 2005-09-06 15:16:25 -0700 | [diff] [blame] | 1226 | wake_futex(this); |
| 1227 | if (++op_ret >= nr_wake2) |
| 1228 | break; |
| 1229 | } |
| 1230 | } |
| 1231 | ret += op_ret; |
| 1232 | } |
| 1233 | |
Darren Hart | aa10990 | 2012-11-26 16:29:56 -0800 | [diff] [blame] | 1234 | out_unlock: |
Darren Hart | 5eb3dc6 | 2009-03-12 00:55:52 -0700 | [diff] [blame] | 1235 | double_unlock_hb(hb1, hb2); |
Darren Hart | 42d35d4 | 2008-12-29 15:49:53 -0800 | [diff] [blame] | 1236 | out_put_keys: |
Thomas Gleixner | ae791a2 | 2010-11-10 13:30:36 +0100 | [diff] [blame] | 1237 | put_futex_key(&key2); |
Darren Hart | 42d35d4 | 2008-12-29 15:49:53 -0800 | [diff] [blame] | 1238 | out_put_key1: |
Thomas Gleixner | ae791a2 | 2010-11-10 13:30:36 +0100 | [diff] [blame] | 1239 | put_futex_key(&key1); |
Darren Hart | 42d35d4 | 2008-12-29 15:49:53 -0800 | [diff] [blame] | 1240 | out: |
Jakub Jelinek | 4732efb | 2005-09-06 15:16:25 -0700 | [diff] [blame] | 1241 | return ret; |
| 1242 | } |
| 1243 | |
Darren Hart | 9121e47 | 2009-04-03 13:40:31 -0700 | [diff] [blame] | 1244 | /** |
| 1245 | * requeue_futex() - Requeue a futex_q from one hb to another |
| 1246 | * @q: the futex_q to requeue |
| 1247 | * @hb1: the source hash_bucket |
| 1248 | * @hb2: the target hash_bucket |
| 1249 | * @key2: the new key for the requeued futex_q |
| 1250 | */ |
| 1251 | static inline |
| 1252 | void requeue_futex(struct futex_q *q, struct futex_hash_bucket *hb1, |
| 1253 | struct futex_hash_bucket *hb2, union futex_key *key2) |
| 1254 | { |
| 1255 | |
| 1256 | /* |
| 1257 | * If key1 and key2 hash to the same bucket, no need to |
| 1258 | * requeue. |
| 1259 | */ |
| 1260 | if (likely(&hb1->chain != &hb2->chain)) { |
| 1261 | plist_del(&q->list, &hb1->chain); |
| 1262 | plist_add(&q->list, &hb2->chain); |
| 1263 | q->lock_ptr = &hb2->lock; |
Darren Hart | 9121e47 | 2009-04-03 13:40:31 -0700 | [diff] [blame] | 1264 | } |
| 1265 | get_futex_key_refs(key2); |
| 1266 | q->key = *key2; |
| 1267 | } |
| 1268 | |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1269 | /** |
| 1270 | * requeue_pi_wake_futex() - Wake a task that acquired the lock during requeue |
Darren Hart | d96ee56 | 2009-09-21 22:30:22 -0700 | [diff] [blame] | 1271 | * @q: the futex_q |
| 1272 | * @key: the key of the requeue target futex |
| 1273 | * @hb: the hash_bucket of the requeue target futex |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1274 | * |
| 1275 | * During futex_requeue, with requeue_pi=1, it is possible to acquire the |
| 1276 | * target futex if it is uncontended or via a lock steal. Set the futex_q key |
| 1277 | * to the requeue target futex so the waiter can detect the wakeup on the right |
| 1278 | * futex, but remove it from the hb and NULL the rt_waiter so it can detect |
Darren Hart | beda2c7 | 2009-08-09 15:34:39 -0700 | [diff] [blame] | 1279 | * atomic lock acquisition. Set the q->lock_ptr to the requeue target hb->lock |
| 1280 | * to protect access to the pi_state to fixup the owner later. Must be called |
| 1281 | * with both q->lock_ptr and hb->lock held. |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1282 | */ |
| 1283 | static inline |
Darren Hart | beda2c7 | 2009-08-09 15:34:39 -0700 | [diff] [blame] | 1284 | void requeue_pi_wake_futex(struct futex_q *q, union futex_key *key, |
| 1285 | struct futex_hash_bucket *hb) |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1286 | { |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1287 | get_futex_key_refs(key); |
| 1288 | q->key = *key; |
| 1289 | |
Lai Jiangshan | 2e12978 | 2010-12-22 14:18:50 +0800 | [diff] [blame] | 1290 | __unqueue_futex(q); |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1291 | |
| 1292 | WARN_ON(!q->rt_waiter); |
| 1293 | q->rt_waiter = NULL; |
| 1294 | |
Darren Hart | beda2c7 | 2009-08-09 15:34:39 -0700 | [diff] [blame] | 1295 | q->lock_ptr = &hb->lock; |
Darren Hart | beda2c7 | 2009-08-09 15:34:39 -0700 | [diff] [blame] | 1296 | |
Thomas Gleixner | f1a11e0 | 2009-05-05 19:21:40 +0200 | [diff] [blame] | 1297 | wake_up_state(q->task, TASK_NORMAL); |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1298 | } |
| 1299 | |
| 1300 | /** |
| 1301 | * futex_proxy_trylock_atomic() - Attempt an atomic lock for the top waiter |
Darren Hart | bab5bc9 | 2009-04-07 23:23:50 -0700 | [diff] [blame] | 1302 | * @pifutex: the user address of the to futex |
| 1303 | * @hb1: the from futex hash bucket, must be locked by the caller |
| 1304 | * @hb2: the to futex hash bucket, must be locked by the caller |
| 1305 | * @key1: the from futex key |
| 1306 | * @key2: the to futex key |
| 1307 | * @ps: address to store the pi_state pointer |
| 1308 | * @set_waiters: force setting the FUTEX_WAITERS bit (1) or not (0) |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1309 | * |
| 1310 | * Try and get the lock on behalf of the top waiter if we can do it atomically. |
Darren Hart | bab5bc9 | 2009-04-07 23:23:50 -0700 | [diff] [blame] | 1311 | * Wake the top waiter if we succeed. If the caller specified set_waiters, |
| 1312 | * then direct futex_lock_pi_atomic() to force setting the FUTEX_WAITERS bit. |
| 1313 | * hb1 and hb2 must be held by the caller. |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1314 | * |
Randy Dunlap | 6c23cbb | 2013-03-05 10:00:24 -0800 | [diff] [blame] | 1315 | * Return: |
| 1316 | * 0 - failed to acquire the lock atomically; |
| 1317 | * 1 - acquired the lock; |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1318 | * <0 - error |
| 1319 | */ |
| 1320 | static int futex_proxy_trylock_atomic(u32 __user *pifutex, |
| 1321 | struct futex_hash_bucket *hb1, |
| 1322 | struct futex_hash_bucket *hb2, |
| 1323 | union futex_key *key1, union futex_key *key2, |
Darren Hart | bab5bc9 | 2009-04-07 23:23:50 -0700 | [diff] [blame] | 1324 | struct futex_pi_state **ps, int set_waiters) |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1325 | { |
Darren Hart | bab5bc9 | 2009-04-07 23:23:50 -0700 | [diff] [blame] | 1326 | struct futex_q *top_waiter = NULL; |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1327 | u32 curval; |
| 1328 | int ret; |
| 1329 | |
| 1330 | if (get_futex_value_locked(&curval, pifutex)) |
| 1331 | return -EFAULT; |
| 1332 | |
Darren Hart | bab5bc9 | 2009-04-07 23:23:50 -0700 | [diff] [blame] | 1333 | /* |
| 1334 | * Find the top_waiter and determine if there are additional waiters. |
| 1335 | * If the caller intends to requeue more than 1 waiter to pifutex, |
| 1336 | * force futex_lock_pi_atomic() to set the FUTEX_WAITERS bit now, |
| 1337 | * as we have means to handle the possible fault. If not, don't set |
| 1338 | * the bit unecessarily as it will force the subsequent unlock to enter |
| 1339 | * the kernel. |
| 1340 | */ |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1341 | top_waiter = futex_top_waiter(hb1, key1); |
| 1342 | |
| 1343 | /* There are no waiters, nothing for us to do. */ |
| 1344 | if (!top_waiter) |
| 1345 | return 0; |
| 1346 | |
Darren Hart | 84bc4af | 2009-08-13 17:36:53 -0700 | [diff] [blame] | 1347 | /* Ensure we requeue to the expected futex. */ |
| 1348 | if (!match_futex(top_waiter->requeue_pi_key, key2)) |
| 1349 | return -EINVAL; |
| 1350 | |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1351 | /* |
Darren Hart | bab5bc9 | 2009-04-07 23:23:50 -0700 | [diff] [blame] | 1352 | * Try to take the lock for top_waiter. Set the FUTEX_WAITERS bit in |
| 1353 | * the contended case or if set_waiters is 1. The pi_state is returned |
| 1354 | * in ps in contended cases. |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1355 | */ |
Darren Hart | bab5bc9 | 2009-04-07 23:23:50 -0700 | [diff] [blame] | 1356 | ret = futex_lock_pi_atomic(pifutex, hb2, key2, ps, top_waiter->task, |
| 1357 | set_waiters); |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1358 | if (ret == 1) |
Darren Hart | beda2c7 | 2009-08-09 15:34:39 -0700 | [diff] [blame] | 1359 | requeue_pi_wake_futex(top_waiter, key2, hb2); |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1360 | |
| 1361 | return ret; |
| 1362 | } |
| 1363 | |
| 1364 | /** |
| 1365 | * futex_requeue() - Requeue waiters from uaddr1 to uaddr2 |
Randy Dunlap | fb62db2 | 2010-10-13 11:02:34 -0700 | [diff] [blame] | 1366 | * @uaddr1: source futex user address |
Darren Hart | b41277d | 2010-11-08 13:10:09 -0800 | [diff] [blame] | 1367 | * @flags: futex flags (FLAGS_SHARED, etc.) |
Randy Dunlap | fb62db2 | 2010-10-13 11:02:34 -0700 | [diff] [blame] | 1368 | * @uaddr2: target futex user address |
| 1369 | * @nr_wake: number of waiters to wake (must be 1 for requeue_pi) |
| 1370 | * @nr_requeue: number of waiters to requeue (0-INT_MAX) |
| 1371 | * @cmpval: @uaddr1 expected value (or %NULL) |
| 1372 | * @requeue_pi: if we are attempting to requeue from a non-pi futex to a |
Darren Hart | b41277d | 2010-11-08 13:10:09 -0800 | [diff] [blame] | 1373 | * pi futex (pi to pi requeue is not supported) |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1374 | * |
| 1375 | * Requeue waiters on uaddr1 to uaddr2. In the requeue_pi case, try to acquire |
| 1376 | * uaddr2 atomically on behalf of the top waiter. |
| 1377 | * |
Randy Dunlap | 6c23cbb | 2013-03-05 10:00:24 -0800 | [diff] [blame] | 1378 | * Return: |
| 1379 | * >=0 - on success, the number of tasks requeued or woken; |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1380 | * <0 - on error |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1381 | */ |
Darren Hart | b41277d | 2010-11-08 13:10:09 -0800 | [diff] [blame] | 1382 | static int futex_requeue(u32 __user *uaddr1, unsigned int flags, |
| 1383 | u32 __user *uaddr2, int nr_wake, int nr_requeue, |
| 1384 | u32 *cmpval, int requeue_pi) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1385 | { |
Peter Zijlstra | 38d47c1 | 2008-09-26 19:32:20 +0200 | [diff] [blame] | 1386 | union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT; |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1387 | int drop_count = 0, task_count = 0, ret; |
| 1388 | struct futex_pi_state *pi_state = NULL; |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 1389 | struct futex_hash_bucket *hb1, *hb2; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1390 | struct futex_q *this, *next; |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1391 | u32 curval2; |
| 1392 | |
| 1393 | if (requeue_pi) { |
| 1394 | /* |
| 1395 | * requeue_pi requires a pi_state, try to allocate it now |
| 1396 | * without any locks in case it fails. |
| 1397 | */ |
| 1398 | if (refill_pi_state_cache()) |
| 1399 | return -ENOMEM; |
| 1400 | /* |
| 1401 | * requeue_pi must wake as many tasks as it can, up to nr_wake |
| 1402 | * + nr_requeue, since it acquires the rt_mutex prior to |
| 1403 | * returning to userspace, so as to not leave the rt_mutex with |
| 1404 | * waiters and no owner. However, second and third wake-ups |
| 1405 | * cannot be predicted as they involve race conditions with the |
| 1406 | * first wake and a fault while looking up the pi_state. Both |
| 1407 | * pthread_cond_signal() and pthread_cond_broadcast() should |
| 1408 | * use nr_wake=1. |
| 1409 | */ |
| 1410 | if (nr_wake != 1) |
| 1411 | return -EINVAL; |
| 1412 | } |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1413 | |
Darren Hart | 42d35d4 | 2008-12-29 15:49:53 -0800 | [diff] [blame] | 1414 | retry: |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1415 | if (pi_state != NULL) { |
| 1416 | /* |
| 1417 | * We will have to lookup the pi_state again, so free this one |
| 1418 | * to keep the accounting correct. |
| 1419 | */ |
| 1420 | free_pi_state(pi_state); |
| 1421 | pi_state = NULL; |
| 1422 | } |
| 1423 | |
Shawn Bohrer | 9ea7150 | 2011-06-30 11:21:32 -0500 | [diff] [blame] | 1424 | ret = get_futex_key(uaddr1, flags & FLAGS_SHARED, &key1, VERIFY_READ); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1425 | if (unlikely(ret != 0)) |
| 1426 | goto out; |
Shawn Bohrer | 9ea7150 | 2011-06-30 11:21:32 -0500 | [diff] [blame] | 1427 | ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2, |
| 1428 | requeue_pi ? VERIFY_WRITE : VERIFY_READ); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1429 | if (unlikely(ret != 0)) |
Darren Hart | 42d35d4 | 2008-12-29 15:49:53 -0800 | [diff] [blame] | 1430 | goto out_put_key1; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1431 | |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 1432 | hb1 = hash_futex(&key1); |
| 1433 | hb2 = hash_futex(&key2); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1434 | |
Darren Hart | e4dc5b7 | 2009-03-12 00:56:13 -0700 | [diff] [blame] | 1435 | retry_private: |
Ingo Molnar | 8b8f319 | 2006-07-03 00:25:05 -0700 | [diff] [blame] | 1436 | double_lock_hb(hb1, hb2); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1437 | |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 1438 | if (likely(cmpval != NULL)) { |
| 1439 | u32 curval; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1440 | |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 1441 | ret = get_futex_value_locked(&curval, uaddr1); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1442 | |
| 1443 | if (unlikely(ret)) { |
Darren Hart | 5eb3dc6 | 2009-03-12 00:55:52 -0700 | [diff] [blame] | 1444 | double_unlock_hb(hb1, hb2); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1445 | |
Darren Hart | e4dc5b7 | 2009-03-12 00:56:13 -0700 | [diff] [blame] | 1446 | ret = get_user(curval, uaddr1); |
| 1447 | if (ret) |
| 1448 | goto out_put_keys; |
| 1449 | |
Darren Hart | b41277d | 2010-11-08 13:10:09 -0800 | [diff] [blame] | 1450 | if (!(flags & FLAGS_SHARED)) |
Darren Hart | e4dc5b7 | 2009-03-12 00:56:13 -0700 | [diff] [blame] | 1451 | goto retry_private; |
| 1452 | |
Thomas Gleixner | ae791a2 | 2010-11-10 13:30:36 +0100 | [diff] [blame] | 1453 | put_futex_key(&key2); |
| 1454 | put_futex_key(&key1); |
Darren Hart | e4dc5b7 | 2009-03-12 00:56:13 -0700 | [diff] [blame] | 1455 | goto retry; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1456 | } |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 1457 | if (curval != *cmpval) { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1458 | ret = -EAGAIN; |
| 1459 | goto out_unlock; |
| 1460 | } |
| 1461 | } |
| 1462 | |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1463 | if (requeue_pi && (task_count - nr_wake < nr_requeue)) { |
Darren Hart | bab5bc9 | 2009-04-07 23:23:50 -0700 | [diff] [blame] | 1464 | /* |
| 1465 | * Attempt to acquire uaddr2 and wake the top waiter. If we |
| 1466 | * intend to requeue waiters, force setting the FUTEX_WAITERS |
| 1467 | * bit. We force this here where we are able to easily handle |
| 1468 | * faults rather in the requeue loop below. |
| 1469 | */ |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1470 | ret = futex_proxy_trylock_atomic(uaddr2, hb1, hb2, &key1, |
Darren Hart | bab5bc9 | 2009-04-07 23:23:50 -0700 | [diff] [blame] | 1471 | &key2, &pi_state, nr_requeue); |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1472 | |
| 1473 | /* |
| 1474 | * At this point the top_waiter has either taken uaddr2 or is |
| 1475 | * waiting on it. If the former, then the pi_state will not |
| 1476 | * exist yet, look it up one more time to ensure we have a |
| 1477 | * reference to it. |
| 1478 | */ |
| 1479 | if (ret == 1) { |
| 1480 | WARN_ON(pi_state); |
Darren Hart | 89061d3 | 2009-10-15 15:30:48 -0700 | [diff] [blame] | 1481 | drop_count++; |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1482 | task_count++; |
| 1483 | ret = get_futex_value_locked(&curval2, uaddr2); |
| 1484 | if (!ret) |
| 1485 | ret = lookup_pi_state(curval2, hb2, &key2, |
| 1486 | &pi_state); |
| 1487 | } |
| 1488 | |
| 1489 | switch (ret) { |
| 1490 | case 0: |
| 1491 | break; |
| 1492 | case -EFAULT: |
| 1493 | double_unlock_hb(hb1, hb2); |
Thomas Gleixner | ae791a2 | 2010-11-10 13:30:36 +0100 | [diff] [blame] | 1494 | put_futex_key(&key2); |
| 1495 | put_futex_key(&key1); |
Thomas Gleixner | d072599 | 2009-06-11 23:15:43 +0200 | [diff] [blame] | 1496 | ret = fault_in_user_writeable(uaddr2); |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1497 | if (!ret) |
| 1498 | goto retry; |
| 1499 | goto out; |
| 1500 | case -EAGAIN: |
| 1501 | /* The owner was exiting, try again. */ |
| 1502 | double_unlock_hb(hb1, hb2); |
Thomas Gleixner | ae791a2 | 2010-11-10 13:30:36 +0100 | [diff] [blame] | 1503 | put_futex_key(&key2); |
| 1504 | put_futex_key(&key1); |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1505 | cond_resched(); |
| 1506 | goto retry; |
| 1507 | default: |
| 1508 | goto out_unlock; |
| 1509 | } |
| 1510 | } |
| 1511 | |
Jason Low | 0d00c7b | 2014-01-12 15:31:22 -0800 | [diff] [blame] | 1512 | plist_for_each_entry_safe(this, next, &hb1->chain, list) { |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1513 | if (task_count - nr_wake >= nr_requeue) |
| 1514 | break; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1515 | |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1516 | if (!match_futex(&this->key, &key1)) |
| 1517 | continue; |
| 1518 | |
Darren Hart | 392741e | 2009-08-07 15:20:48 -0700 | [diff] [blame] | 1519 | /* |
| 1520 | * FUTEX_WAIT_REQEUE_PI and FUTEX_CMP_REQUEUE_PI should always |
| 1521 | * be paired with each other and no other futex ops. |
Darren Hart | aa10990 | 2012-11-26 16:29:56 -0800 | [diff] [blame] | 1522 | * |
| 1523 | * We should never be requeueing a futex_q with a pi_state, |
| 1524 | * which is awaiting a futex_unlock_pi(). |
Darren Hart | 392741e | 2009-08-07 15:20:48 -0700 | [diff] [blame] | 1525 | */ |
| 1526 | if ((requeue_pi && !this->rt_waiter) || |
Darren Hart | aa10990 | 2012-11-26 16:29:56 -0800 | [diff] [blame] | 1527 | (!requeue_pi && this->rt_waiter) || |
| 1528 | this->pi_state) { |
Darren Hart | 392741e | 2009-08-07 15:20:48 -0700 | [diff] [blame] | 1529 | ret = -EINVAL; |
| 1530 | break; |
| 1531 | } |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1532 | |
| 1533 | /* |
| 1534 | * Wake nr_wake waiters. For requeue_pi, if we acquired the |
| 1535 | * lock, we already woke the top_waiter. If not, it will be |
| 1536 | * woken by futex_unlock_pi(). |
| 1537 | */ |
| 1538 | if (++task_count <= nr_wake && !requeue_pi) { |
| 1539 | wake_futex(this); |
| 1540 | continue; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1541 | } |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1542 | |
Darren Hart | 84bc4af | 2009-08-13 17:36:53 -0700 | [diff] [blame] | 1543 | /* Ensure we requeue to the expected futex for requeue_pi. */ |
| 1544 | if (requeue_pi && !match_futex(this->requeue_pi_key, &key2)) { |
| 1545 | ret = -EINVAL; |
| 1546 | break; |
| 1547 | } |
| 1548 | |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1549 | /* |
| 1550 | * Requeue nr_requeue waiters and possibly one more in the case |
| 1551 | * of requeue_pi if we couldn't acquire the lock atomically. |
| 1552 | */ |
| 1553 | if (requeue_pi) { |
| 1554 | /* Prepare the waiter to take the rt_mutex. */ |
| 1555 | atomic_inc(&pi_state->refcount); |
| 1556 | this->pi_state = pi_state; |
| 1557 | ret = rt_mutex_start_proxy_lock(&pi_state->pi_mutex, |
| 1558 | this->rt_waiter, |
| 1559 | this->task, 1); |
| 1560 | if (ret == 1) { |
| 1561 | /* We got the lock. */ |
Darren Hart | beda2c7 | 2009-08-09 15:34:39 -0700 | [diff] [blame] | 1562 | requeue_pi_wake_futex(this, &key2, hb2); |
Darren Hart | 89061d3 | 2009-10-15 15:30:48 -0700 | [diff] [blame] | 1563 | drop_count++; |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1564 | continue; |
| 1565 | } else if (ret) { |
| 1566 | /* -EDEADLK */ |
| 1567 | this->pi_state = NULL; |
| 1568 | free_pi_state(pi_state); |
| 1569 | goto out_unlock; |
| 1570 | } |
| 1571 | } |
| 1572 | requeue_futex(this, hb1, hb2, &key2); |
| 1573 | drop_count++; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1574 | } |
| 1575 | |
| 1576 | out_unlock: |
Darren Hart | 5eb3dc6 | 2009-03-12 00:55:52 -0700 | [diff] [blame] | 1577 | double_unlock_hb(hb1, hb2); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1578 | |
Darren Hart | cd84a42 | 2009-04-02 14:19:38 -0700 | [diff] [blame] | 1579 | /* |
| 1580 | * drop_futex_key_refs() must be called outside the spinlocks. During |
| 1581 | * the requeue we moved futex_q's from the hash bucket at key1 to the |
| 1582 | * one at key2 and updated their key pointer. We no longer need to |
| 1583 | * hold the references to key1. |
| 1584 | */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1585 | while (--drop_count >= 0) |
Rusty Russell | 9adef58 | 2007-05-08 00:26:42 -0700 | [diff] [blame] | 1586 | drop_futex_key_refs(&key1); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1587 | |
Darren Hart | 42d35d4 | 2008-12-29 15:49:53 -0800 | [diff] [blame] | 1588 | out_put_keys: |
Thomas Gleixner | ae791a2 | 2010-11-10 13:30:36 +0100 | [diff] [blame] | 1589 | put_futex_key(&key2); |
Darren Hart | 42d35d4 | 2008-12-29 15:49:53 -0800 | [diff] [blame] | 1590 | out_put_key1: |
Thomas Gleixner | ae791a2 | 2010-11-10 13:30:36 +0100 | [diff] [blame] | 1591 | put_futex_key(&key1); |
Darren Hart | 42d35d4 | 2008-12-29 15:49:53 -0800 | [diff] [blame] | 1592 | out: |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 1593 | if (pi_state != NULL) |
| 1594 | free_pi_state(pi_state); |
| 1595 | return ret ? ret : task_count; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1596 | } |
| 1597 | |
| 1598 | /* The key must be already stored in q->key. */ |
Eric Sesterhenn | 82af7ac | 2008-01-25 10:40:46 +0100 | [diff] [blame] | 1599 | static inline struct futex_hash_bucket *queue_lock(struct futex_q *q) |
Namhyung Kim | 15e408c | 2010-09-14 21:43:48 +0900 | [diff] [blame] | 1600 | __acquires(&hb->lock) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1601 | { |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 1602 | struct futex_hash_bucket *hb; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1603 | |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 1604 | hb = hash_futex(&q->key); |
| 1605 | q->lock_ptr = &hb->lock; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1606 | |
Davidlohr Bueso | b0c29f7 | 2014-01-12 15:31:25 -0800 | [diff] [blame] | 1607 | spin_lock(&hb->lock); /* implies MB (A) */ |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 1608 | return hb; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1609 | } |
| 1610 | |
Darren Hart | d40d65c | 2009-09-21 22:30:15 -0700 | [diff] [blame] | 1611 | static inline void |
Jason Low | 0d00c7b | 2014-01-12 15:31:22 -0800 | [diff] [blame] | 1612 | queue_unlock(struct futex_hash_bucket *hb) |
Namhyung Kim | 15e408c | 2010-09-14 21:43:48 +0900 | [diff] [blame] | 1613 | __releases(&hb->lock) |
Darren Hart | d40d65c | 2009-09-21 22:30:15 -0700 | [diff] [blame] | 1614 | { |
| 1615 | spin_unlock(&hb->lock); |
Darren Hart | d40d65c | 2009-09-21 22:30:15 -0700 | [diff] [blame] | 1616 | } |
| 1617 | |
| 1618 | /** |
| 1619 | * queue_me() - Enqueue the futex_q on the futex_hash_bucket |
| 1620 | * @q: The futex_q to enqueue |
| 1621 | * @hb: The destination hash bucket |
| 1622 | * |
| 1623 | * The hb->lock must be held by the caller, and is released here. A call to |
| 1624 | * queue_me() is typically paired with exactly one call to unqueue_me(). The |
| 1625 | * exceptions involve the PI related operations, which may use unqueue_me_pi() |
| 1626 | * or nothing if the unqueue is done as part of the wake process and the unqueue |
| 1627 | * state is implicit in the state of woken task (see futex_wait_requeue_pi() for |
| 1628 | * an example). |
| 1629 | */ |
Eric Sesterhenn | 82af7ac | 2008-01-25 10:40:46 +0100 | [diff] [blame] | 1630 | static inline void queue_me(struct futex_q *q, struct futex_hash_bucket *hb) |
Namhyung Kim | 15e408c | 2010-09-14 21:43:48 +0900 | [diff] [blame] | 1631 | __releases(&hb->lock) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1632 | { |
Pierre Peiffer | ec92d08 | 2007-05-09 02:35:00 -0700 | [diff] [blame] | 1633 | int prio; |
| 1634 | |
| 1635 | /* |
| 1636 | * The priority used to register this element is |
| 1637 | * - either the real thread-priority for the real-time threads |
| 1638 | * (i.e. threads with a priority lower than MAX_RT_PRIO) |
| 1639 | * - or MAX_RT_PRIO for non-RT threads. |
| 1640 | * Thus, all RT-threads are woken first in priority order, and |
| 1641 | * the others are woken last, in FIFO order. |
| 1642 | */ |
| 1643 | prio = min(current->normal_prio, MAX_RT_PRIO); |
| 1644 | |
| 1645 | plist_node_init(&q->list, prio); |
Pierre Peiffer | ec92d08 | 2007-05-09 02:35:00 -0700 | [diff] [blame] | 1646 | plist_add(&q->list, &hb->chain); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1647 | q->task = current; |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 1648 | spin_unlock(&hb->lock); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1649 | } |
| 1650 | |
Darren Hart | d40d65c | 2009-09-21 22:30:15 -0700 | [diff] [blame] | 1651 | /** |
| 1652 | * unqueue_me() - Remove the futex_q from its futex_hash_bucket |
| 1653 | * @q: The futex_q to unqueue |
| 1654 | * |
| 1655 | * The q->lock_ptr must not be held by the caller. A call to unqueue_me() must |
| 1656 | * be paired with exactly one earlier call to queue_me(). |
| 1657 | * |
Randy Dunlap | 6c23cbb | 2013-03-05 10:00:24 -0800 | [diff] [blame] | 1658 | * Return: |
| 1659 | * 1 - if the futex_q was still queued (and we removed unqueued it); |
Darren Hart | d40d65c | 2009-09-21 22:30:15 -0700 | [diff] [blame] | 1660 | * 0 - if the futex_q was already removed by the waking thread |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1661 | */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1662 | static int unqueue_me(struct futex_q *q) |
| 1663 | { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1664 | spinlock_t *lock_ptr; |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 1665 | int ret = 0; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1666 | |
| 1667 | /* In the common case we don't take the spinlock, which is nice. */ |
Darren Hart | 42d35d4 | 2008-12-29 15:49:53 -0800 | [diff] [blame] | 1668 | retry: |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1669 | lock_ptr = q->lock_ptr; |
Christian Borntraeger | e91467e | 2006-08-05 12:13:52 -0700 | [diff] [blame] | 1670 | barrier(); |
Stephen Hemminger | c80544d | 2007-10-18 03:07:05 -0700 | [diff] [blame] | 1671 | if (lock_ptr != NULL) { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1672 | spin_lock(lock_ptr); |
| 1673 | /* |
| 1674 | * q->lock_ptr can change between reading it and |
| 1675 | * spin_lock(), causing us to take the wrong lock. This |
| 1676 | * corrects the race condition. |
| 1677 | * |
| 1678 | * Reasoning goes like this: if we have the wrong lock, |
| 1679 | * q->lock_ptr must have changed (maybe several times) |
| 1680 | * between reading it and the spin_lock(). It can |
| 1681 | * change again after the spin_lock() but only if it was |
| 1682 | * already changed before the spin_lock(). It cannot, |
| 1683 | * however, change back to the original value. Therefore |
| 1684 | * we can detect whether we acquired the correct lock. |
| 1685 | */ |
| 1686 | if (unlikely(lock_ptr != q->lock_ptr)) { |
| 1687 | spin_unlock(lock_ptr); |
| 1688 | goto retry; |
| 1689 | } |
Lai Jiangshan | 2e12978 | 2010-12-22 14:18:50 +0800 | [diff] [blame] | 1690 | __unqueue_futex(q); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1691 | |
| 1692 | BUG_ON(q->pi_state); |
| 1693 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1694 | spin_unlock(lock_ptr); |
| 1695 | ret = 1; |
| 1696 | } |
| 1697 | |
Rusty Russell | 9adef58 | 2007-05-08 00:26:42 -0700 | [diff] [blame] | 1698 | drop_futex_key_refs(&q->key); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1699 | return ret; |
| 1700 | } |
| 1701 | |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1702 | /* |
| 1703 | * PI futexes can not be requeued and must remove themself from the |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 1704 | * hash bucket. The hash bucket lock (i.e. lock_ptr) is held on entry |
| 1705 | * and dropped here. |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1706 | */ |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 1707 | static void unqueue_me_pi(struct futex_q *q) |
Namhyung Kim | 15e408c | 2010-09-14 21:43:48 +0900 | [diff] [blame] | 1708 | __releases(q->lock_ptr) |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1709 | { |
Lai Jiangshan | 2e12978 | 2010-12-22 14:18:50 +0800 | [diff] [blame] | 1710 | __unqueue_futex(q); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1711 | |
| 1712 | BUG_ON(!q->pi_state); |
| 1713 | free_pi_state(q->pi_state); |
| 1714 | q->pi_state = NULL; |
| 1715 | |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 1716 | spin_unlock(q->lock_ptr); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 1717 | } |
| 1718 | |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 1719 | /* |
Thomas Gleixner | cdf71a1 | 2008-01-08 19:47:38 +0100 | [diff] [blame] | 1720 | * Fixup the pi_state owner with the new owner. |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 1721 | * |
Alexey Kuznetsov | 778e9a9 | 2007-06-08 13:47:00 -0700 | [diff] [blame] | 1722 | * Must be called with hash bucket lock held and mm->sem held for non |
| 1723 | * private futexes. |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 1724 | */ |
Alexey Kuznetsov | 778e9a9 | 2007-06-08 13:47:00 -0700 | [diff] [blame] | 1725 | static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q, |
Thomas Gleixner | ae791a2 | 2010-11-10 13:30:36 +0100 | [diff] [blame] | 1726 | struct task_struct *newowner) |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 1727 | { |
Thomas Gleixner | cdf71a1 | 2008-01-08 19:47:38 +0100 | [diff] [blame] | 1728 | u32 newtid = task_pid_vnr(newowner) | FUTEX_WAITERS; |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 1729 | struct futex_pi_state *pi_state = q->pi_state; |
Thomas Gleixner | 1b7558e | 2008-06-23 11:21:58 +0200 | [diff] [blame] | 1730 | struct task_struct *oldowner = pi_state->owner; |
Vitaliy Ivanov | 7cfdaf3 | 2011-07-07 15:10:31 +0300 | [diff] [blame] | 1731 | u32 uval, uninitialized_var(curval), newval; |
Darren Hart | e4dc5b7 | 2009-03-12 00:56:13 -0700 | [diff] [blame] | 1732 | int ret; |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 1733 | |
| 1734 | /* Owner died? */ |
Thomas Gleixner | 1b7558e | 2008-06-23 11:21:58 +0200 | [diff] [blame] | 1735 | if (!pi_state->owner) |
| 1736 | newtid |= FUTEX_OWNER_DIED; |
| 1737 | |
| 1738 | /* |
| 1739 | * We are here either because we stole the rtmutex from the |
Lai Jiangshan | 8161239 | 2011-01-14 17:09:41 +0800 | [diff] [blame] | 1740 | * previous highest priority waiter or we are the highest priority |
| 1741 | * waiter but failed to get the rtmutex the first time. |
| 1742 | * We have to replace the newowner TID in the user space variable. |
| 1743 | * This must be atomic as we have to preserve the owner died bit here. |
Thomas Gleixner | 1b7558e | 2008-06-23 11:21:58 +0200 | [diff] [blame] | 1744 | * |
Darren Hart | b2d0994 | 2009-03-12 00:55:37 -0700 | [diff] [blame] | 1745 | * Note: We write the user space value _before_ changing the pi_state |
| 1746 | * because we can fault here. Imagine swapped out pages or a fork |
| 1747 | * that marked all the anonymous memory readonly for cow. |
Thomas Gleixner | 1b7558e | 2008-06-23 11:21:58 +0200 | [diff] [blame] | 1748 | * |
| 1749 | * Modifying pi_state _before_ the user space value would |
| 1750 | * leave the pi_state in an inconsistent state when we fault |
| 1751 | * here, because we need to drop the hash bucket lock to |
| 1752 | * handle the fault. This might be observed in the PID check |
| 1753 | * in lookup_pi_state. |
| 1754 | */ |
| 1755 | retry: |
| 1756 | if (get_futex_value_locked(&uval, uaddr)) |
| 1757 | goto handle_fault; |
| 1758 | |
| 1759 | while (1) { |
| 1760 | newval = (uval & FUTEX_OWNER_DIED) | newtid; |
| 1761 | |
Michel Lespinasse | 37a9d91 | 2011-03-10 18:48:51 -0800 | [diff] [blame] | 1762 | if (cmpxchg_futex_value_locked(&curval, uaddr, uval, newval)) |
Thomas Gleixner | 1b7558e | 2008-06-23 11:21:58 +0200 | [diff] [blame] | 1763 | goto handle_fault; |
| 1764 | if (curval == uval) |
| 1765 | break; |
| 1766 | uval = curval; |
| 1767 | } |
| 1768 | |
| 1769 | /* |
| 1770 | * We fixed up user space. Now we need to fix the pi_state |
| 1771 | * itself. |
| 1772 | */ |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 1773 | if (pi_state->owner != NULL) { |
Thomas Gleixner | 1d61548 | 2009-11-17 14:54:03 +0100 | [diff] [blame] | 1774 | raw_spin_lock_irq(&pi_state->owner->pi_lock); |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 1775 | WARN_ON(list_empty(&pi_state->list)); |
| 1776 | list_del_init(&pi_state->list); |
Thomas Gleixner | 1d61548 | 2009-11-17 14:54:03 +0100 | [diff] [blame] | 1777 | raw_spin_unlock_irq(&pi_state->owner->pi_lock); |
Thomas Gleixner | 1b7558e | 2008-06-23 11:21:58 +0200 | [diff] [blame] | 1778 | } |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 1779 | |
Thomas Gleixner | cdf71a1 | 2008-01-08 19:47:38 +0100 | [diff] [blame] | 1780 | pi_state->owner = newowner; |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 1781 | |
Thomas Gleixner | 1d61548 | 2009-11-17 14:54:03 +0100 | [diff] [blame] | 1782 | raw_spin_lock_irq(&newowner->pi_lock); |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 1783 | WARN_ON(!list_empty(&pi_state->list)); |
Thomas Gleixner | cdf71a1 | 2008-01-08 19:47:38 +0100 | [diff] [blame] | 1784 | list_add(&pi_state->list, &newowner->pi_state_list); |
Thomas Gleixner | 1d61548 | 2009-11-17 14:54:03 +0100 | [diff] [blame] | 1785 | raw_spin_unlock_irq(&newowner->pi_lock); |
Thomas Gleixner | 1b7558e | 2008-06-23 11:21:58 +0200 | [diff] [blame] | 1786 | return 0; |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 1787 | |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 1788 | /* |
Thomas Gleixner | 1b7558e | 2008-06-23 11:21:58 +0200 | [diff] [blame] | 1789 | * To handle the page fault we need to drop the hash bucket |
Lai Jiangshan | 8161239 | 2011-01-14 17:09:41 +0800 | [diff] [blame] | 1790 | * lock here. That gives the other task (either the highest priority |
| 1791 | * waiter itself or the task which stole the rtmutex) the |
Thomas Gleixner | 1b7558e | 2008-06-23 11:21:58 +0200 | [diff] [blame] | 1792 | * chance to try the fixup of the pi_state. So once we are |
| 1793 | * back from handling the fault we need to check the pi_state |
| 1794 | * after reacquiring the hash bucket lock and before trying to |
| 1795 | * do another fixup. When the fixup has been done already we |
| 1796 | * simply return. |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 1797 | */ |
Thomas Gleixner | 1b7558e | 2008-06-23 11:21:58 +0200 | [diff] [blame] | 1798 | handle_fault: |
| 1799 | spin_unlock(q->lock_ptr); |
Alexey Kuznetsov | 778e9a9 | 2007-06-08 13:47:00 -0700 | [diff] [blame] | 1800 | |
Thomas Gleixner | d072599 | 2009-06-11 23:15:43 +0200 | [diff] [blame] | 1801 | ret = fault_in_user_writeable(uaddr); |
Alexey Kuznetsov | 778e9a9 | 2007-06-08 13:47:00 -0700 | [diff] [blame] | 1802 | |
Thomas Gleixner | 1b7558e | 2008-06-23 11:21:58 +0200 | [diff] [blame] | 1803 | spin_lock(q->lock_ptr); |
Alexey Kuznetsov | 778e9a9 | 2007-06-08 13:47:00 -0700 | [diff] [blame] | 1804 | |
Thomas Gleixner | 1b7558e | 2008-06-23 11:21:58 +0200 | [diff] [blame] | 1805 | /* |
| 1806 | * Check if someone else fixed it for us: |
| 1807 | */ |
| 1808 | if (pi_state->owner != oldowner) |
| 1809 | return 0; |
| 1810 | |
| 1811 | if (ret) |
| 1812 | return ret; |
| 1813 | |
| 1814 | goto retry; |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 1815 | } |
| 1816 | |
Nick Piggin | 72c1bbf | 2007-05-08 00:26:43 -0700 | [diff] [blame] | 1817 | static long futex_wait_restart(struct restart_block *restart); |
Thomas Gleixner | 36cf3b5 | 2007-07-15 23:41:20 -0700 | [diff] [blame] | 1818 | |
Darren Hart | ca5f952 | 2009-04-03 13:39:33 -0700 | [diff] [blame] | 1819 | /** |
Darren Hart | dd97399 | 2009-04-03 13:40:02 -0700 | [diff] [blame] | 1820 | * fixup_owner() - Post lock pi_state and corner case management |
| 1821 | * @uaddr: user address of the futex |
Darren Hart | dd97399 | 2009-04-03 13:40:02 -0700 | [diff] [blame] | 1822 | * @q: futex_q (contains pi_state and access to the rt_mutex) |
| 1823 | * @locked: if the attempt to take the rt_mutex succeeded (1) or not (0) |
| 1824 | * |
| 1825 | * After attempting to lock an rt_mutex, this function is called to cleanup |
| 1826 | * the pi_state owner as well as handle race conditions that may allow us to |
| 1827 | * acquire the lock. Must be called with the hb lock held. |
| 1828 | * |
Randy Dunlap | 6c23cbb | 2013-03-05 10:00:24 -0800 | [diff] [blame] | 1829 | * Return: |
| 1830 | * 1 - success, lock taken; |
| 1831 | * 0 - success, lock not taken; |
Darren Hart | dd97399 | 2009-04-03 13:40:02 -0700 | [diff] [blame] | 1832 | * <0 - on error (-EFAULT) |
| 1833 | */ |
Thomas Gleixner | ae791a2 | 2010-11-10 13:30:36 +0100 | [diff] [blame] | 1834 | static int fixup_owner(u32 __user *uaddr, struct futex_q *q, int locked) |
Darren Hart | dd97399 | 2009-04-03 13:40:02 -0700 | [diff] [blame] | 1835 | { |
| 1836 | struct task_struct *owner; |
| 1837 | int ret = 0; |
| 1838 | |
| 1839 | if (locked) { |
| 1840 | /* |
| 1841 | * Got the lock. We might not be the anticipated owner if we |
| 1842 | * did a lock-steal - fix up the PI-state in that case: |
| 1843 | */ |
| 1844 | if (q->pi_state->owner != current) |
Thomas Gleixner | ae791a2 | 2010-11-10 13:30:36 +0100 | [diff] [blame] | 1845 | ret = fixup_pi_state_owner(uaddr, q, current); |
Darren Hart | dd97399 | 2009-04-03 13:40:02 -0700 | [diff] [blame] | 1846 | goto out; |
| 1847 | } |
| 1848 | |
| 1849 | /* |
| 1850 | * Catch the rare case, where the lock was released when we were on the |
| 1851 | * way back before we locked the hash bucket. |
| 1852 | */ |
| 1853 | if (q->pi_state->owner == current) { |
| 1854 | /* |
| 1855 | * Try to get the rt_mutex now. This might fail as some other |
| 1856 | * task acquired the rt_mutex after we removed ourself from the |
| 1857 | * rt_mutex waiters list. |
| 1858 | */ |
| 1859 | if (rt_mutex_trylock(&q->pi_state->pi_mutex)) { |
| 1860 | locked = 1; |
| 1861 | goto out; |
| 1862 | } |
| 1863 | |
| 1864 | /* |
| 1865 | * pi_state is incorrect, some other task did a lock steal and |
| 1866 | * we returned due to timeout or signal without taking the |
Lai Jiangshan | 8161239 | 2011-01-14 17:09:41 +0800 | [diff] [blame] | 1867 | * rt_mutex. Too late. |
Darren Hart | dd97399 | 2009-04-03 13:40:02 -0700 | [diff] [blame] | 1868 | */ |
Lai Jiangshan | 8161239 | 2011-01-14 17:09:41 +0800 | [diff] [blame] | 1869 | raw_spin_lock(&q->pi_state->pi_mutex.wait_lock); |
Darren Hart | dd97399 | 2009-04-03 13:40:02 -0700 | [diff] [blame] | 1870 | owner = rt_mutex_owner(&q->pi_state->pi_mutex); |
Lai Jiangshan | 8161239 | 2011-01-14 17:09:41 +0800 | [diff] [blame] | 1871 | if (!owner) |
| 1872 | owner = rt_mutex_next_owner(&q->pi_state->pi_mutex); |
| 1873 | raw_spin_unlock(&q->pi_state->pi_mutex.wait_lock); |
Thomas Gleixner | ae791a2 | 2010-11-10 13:30:36 +0100 | [diff] [blame] | 1874 | ret = fixup_pi_state_owner(uaddr, q, owner); |
Darren Hart | dd97399 | 2009-04-03 13:40:02 -0700 | [diff] [blame] | 1875 | goto out; |
| 1876 | } |
| 1877 | |
| 1878 | /* |
| 1879 | * Paranoia check. If we did not take the lock, then we should not be |
Lai Jiangshan | 8161239 | 2011-01-14 17:09:41 +0800 | [diff] [blame] | 1880 | * the owner of the rt_mutex. |
Darren Hart | dd97399 | 2009-04-03 13:40:02 -0700 | [diff] [blame] | 1881 | */ |
| 1882 | if (rt_mutex_owner(&q->pi_state->pi_mutex) == current) |
| 1883 | printk(KERN_ERR "fixup_owner: ret = %d pi-mutex: %p " |
| 1884 | "pi-state %p\n", ret, |
| 1885 | q->pi_state->pi_mutex.owner, |
| 1886 | q->pi_state->owner); |
| 1887 | |
| 1888 | out: |
| 1889 | return ret ? ret : locked; |
| 1890 | } |
| 1891 | |
| 1892 | /** |
Darren Hart | ca5f952 | 2009-04-03 13:39:33 -0700 | [diff] [blame] | 1893 | * futex_wait_queue_me() - queue_me() and wait for wakeup, timeout, or signal |
| 1894 | * @hb: the futex hash bucket, must be locked by the caller |
| 1895 | * @q: the futex_q to queue up on |
| 1896 | * @timeout: the prepared hrtimer_sleeper, or null for no timeout |
Darren Hart | ca5f952 | 2009-04-03 13:39:33 -0700 | [diff] [blame] | 1897 | */ |
| 1898 | static void futex_wait_queue_me(struct futex_hash_bucket *hb, struct futex_q *q, |
Thomas Gleixner | f1a11e0 | 2009-05-05 19:21:40 +0200 | [diff] [blame] | 1899 | struct hrtimer_sleeper *timeout) |
Darren Hart | ca5f952 | 2009-04-03 13:39:33 -0700 | [diff] [blame] | 1900 | { |
Darren Hart | 9beba3c | 2009-09-24 11:54:47 -0700 | [diff] [blame] | 1901 | /* |
| 1902 | * The task state is guaranteed to be set before another task can |
| 1903 | * wake it. set_current_state() is implemented using set_mb() and |
| 1904 | * queue_me() calls spin_unlock() upon completion, both serializing |
| 1905 | * access to the hash list and forcing another memory barrier. |
| 1906 | */ |
Thomas Gleixner | f1a11e0 | 2009-05-05 19:21:40 +0200 | [diff] [blame] | 1907 | set_current_state(TASK_INTERRUPTIBLE); |
Darren Hart | 0729e19 | 2009-09-21 22:30:38 -0700 | [diff] [blame] | 1908 | queue_me(q, hb); |
Darren Hart | ca5f952 | 2009-04-03 13:39:33 -0700 | [diff] [blame] | 1909 | |
| 1910 | /* Arm the timer */ |
| 1911 | if (timeout) { |
| 1912 | hrtimer_start_expires(&timeout->timer, HRTIMER_MODE_ABS); |
| 1913 | if (!hrtimer_active(&timeout->timer)) |
| 1914 | timeout->task = NULL; |
| 1915 | } |
| 1916 | |
| 1917 | /* |
Darren Hart | 0729e19 | 2009-09-21 22:30:38 -0700 | [diff] [blame] | 1918 | * If we have been removed from the hash list, then another task |
| 1919 | * has tried to wake us, and we can skip the call to schedule(). |
Darren Hart | ca5f952 | 2009-04-03 13:39:33 -0700 | [diff] [blame] | 1920 | */ |
| 1921 | if (likely(!plist_node_empty(&q->list))) { |
| 1922 | /* |
| 1923 | * If the timer has already expired, current will already be |
| 1924 | * flagged for rescheduling. Only call schedule if there |
| 1925 | * is no timeout, or if it has yet to expire. |
| 1926 | */ |
| 1927 | if (!timeout || timeout->task) |
Colin Cross | 88c8004 | 2013-05-01 18:35:05 -0700 | [diff] [blame] | 1928 | freezable_schedule(); |
Darren Hart | ca5f952 | 2009-04-03 13:39:33 -0700 | [diff] [blame] | 1929 | } |
| 1930 | __set_current_state(TASK_RUNNING); |
| 1931 | } |
| 1932 | |
Darren Hart | f801073 | 2009-04-03 13:40:40 -0700 | [diff] [blame] | 1933 | /** |
| 1934 | * futex_wait_setup() - Prepare to wait on a futex |
| 1935 | * @uaddr: the futex userspace address |
| 1936 | * @val: the expected value |
Darren Hart | b41277d | 2010-11-08 13:10:09 -0800 | [diff] [blame] | 1937 | * @flags: futex flags (FLAGS_SHARED, etc.) |
Darren Hart | f801073 | 2009-04-03 13:40:40 -0700 | [diff] [blame] | 1938 | * @q: the associated futex_q |
| 1939 | * @hb: storage for hash_bucket pointer to be returned to caller |
| 1940 | * |
| 1941 | * Setup the futex_q and locate the hash_bucket. Get the futex value and |
| 1942 | * compare it with the expected value. Handle atomic faults internally. |
| 1943 | * Return with the hb lock held and a q.key reference on success, and unlocked |
| 1944 | * with no q.key reference on failure. |
| 1945 | * |
Randy Dunlap | 6c23cbb | 2013-03-05 10:00:24 -0800 | [diff] [blame] | 1946 | * Return: |
| 1947 | * 0 - uaddr contains val and hb has been locked; |
Bart Van Assche | ca4a04c | 2011-07-17 09:01:00 +0200 | [diff] [blame] | 1948 | * <1 - -EFAULT or -EWOULDBLOCK (uaddr does not contain val) and hb is unlocked |
Darren Hart | f801073 | 2009-04-03 13:40:40 -0700 | [diff] [blame] | 1949 | */ |
Darren Hart | b41277d | 2010-11-08 13:10:09 -0800 | [diff] [blame] | 1950 | static int futex_wait_setup(u32 __user *uaddr, u32 val, unsigned int flags, |
Darren Hart | f801073 | 2009-04-03 13:40:40 -0700 | [diff] [blame] | 1951 | struct futex_q *q, struct futex_hash_bucket **hb) |
| 1952 | { |
| 1953 | u32 uval; |
| 1954 | int ret; |
| 1955 | |
| 1956 | /* |
| 1957 | * Access the page AFTER the hash-bucket is locked. |
| 1958 | * Order is important: |
| 1959 | * |
| 1960 | * Userspace waiter: val = var; if (cond(val)) futex_wait(&var, val); |
| 1961 | * Userspace waker: if (cond(var)) { var = new; futex_wake(&var); } |
| 1962 | * |
| 1963 | * The basic logical guarantee of a futex is that it blocks ONLY |
| 1964 | * if cond(var) is known to be true at the time of blocking, for |
Michel Lespinasse | 8fe8f54 | 2011-03-06 18:07:50 -0800 | [diff] [blame] | 1965 | * any cond. If we locked the hash-bucket after testing *uaddr, that |
| 1966 | * would open a race condition where we could block indefinitely with |
Darren Hart | f801073 | 2009-04-03 13:40:40 -0700 | [diff] [blame] | 1967 | * cond(var) false, which would violate the guarantee. |
| 1968 | * |
Michel Lespinasse | 8fe8f54 | 2011-03-06 18:07:50 -0800 | [diff] [blame] | 1969 | * On the other hand, we insert q and release the hash-bucket only |
| 1970 | * after testing *uaddr. This guarantees that futex_wait() will NOT |
| 1971 | * absorb a wakeup if *uaddr does not match the desired values |
| 1972 | * while the syscall executes. |
Darren Hart | f801073 | 2009-04-03 13:40:40 -0700 | [diff] [blame] | 1973 | */ |
| 1974 | retry: |
Shawn Bohrer | 9ea7150 | 2011-06-30 11:21:32 -0500 | [diff] [blame] | 1975 | ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &q->key, VERIFY_READ); |
Darren Hart | f801073 | 2009-04-03 13:40:40 -0700 | [diff] [blame] | 1976 | if (unlikely(ret != 0)) |
Darren Hart | a5a2a0c | 2009-04-10 09:50:05 -0700 | [diff] [blame] | 1977 | return ret; |
Darren Hart | f801073 | 2009-04-03 13:40:40 -0700 | [diff] [blame] | 1978 | |
| 1979 | retry_private: |
| 1980 | *hb = queue_lock(q); |
| 1981 | |
| 1982 | ret = get_futex_value_locked(&uval, uaddr); |
| 1983 | |
| 1984 | if (ret) { |
Jason Low | 0d00c7b | 2014-01-12 15:31:22 -0800 | [diff] [blame] | 1985 | queue_unlock(*hb); |
Darren Hart | f801073 | 2009-04-03 13:40:40 -0700 | [diff] [blame] | 1986 | |
| 1987 | ret = get_user(uval, uaddr); |
| 1988 | if (ret) |
| 1989 | goto out; |
| 1990 | |
Darren Hart | b41277d | 2010-11-08 13:10:09 -0800 | [diff] [blame] | 1991 | if (!(flags & FLAGS_SHARED)) |
Darren Hart | f801073 | 2009-04-03 13:40:40 -0700 | [diff] [blame] | 1992 | goto retry_private; |
| 1993 | |
Thomas Gleixner | ae791a2 | 2010-11-10 13:30:36 +0100 | [diff] [blame] | 1994 | put_futex_key(&q->key); |
Darren Hart | f801073 | 2009-04-03 13:40:40 -0700 | [diff] [blame] | 1995 | goto retry; |
| 1996 | } |
| 1997 | |
| 1998 | if (uval != val) { |
Jason Low | 0d00c7b | 2014-01-12 15:31:22 -0800 | [diff] [blame] | 1999 | queue_unlock(*hb); |
Darren Hart | f801073 | 2009-04-03 13:40:40 -0700 | [diff] [blame] | 2000 | ret = -EWOULDBLOCK; |
| 2001 | } |
| 2002 | |
| 2003 | out: |
| 2004 | if (ret) |
Thomas Gleixner | ae791a2 | 2010-11-10 13:30:36 +0100 | [diff] [blame] | 2005 | put_futex_key(&q->key); |
Darren Hart | f801073 | 2009-04-03 13:40:40 -0700 | [diff] [blame] | 2006 | return ret; |
| 2007 | } |
| 2008 | |
Darren Hart | b41277d | 2010-11-08 13:10:09 -0800 | [diff] [blame] | 2009 | static int futex_wait(u32 __user *uaddr, unsigned int flags, u32 val, |
| 2010 | ktime_t *abs_time, u32 bitset) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2011 | { |
Darren Hart | ca5f952 | 2009-04-03 13:39:33 -0700 | [diff] [blame] | 2012 | struct hrtimer_sleeper timeout, *to = NULL; |
Peter Zijlstra | 2fff78c | 2009-02-11 18:10:10 +0100 | [diff] [blame] | 2013 | struct restart_block *restart; |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 2014 | struct futex_hash_bucket *hb; |
Darren Hart | 5bdb05f | 2010-11-08 13:40:28 -0800 | [diff] [blame] | 2015 | struct futex_q q = futex_q_init; |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 2016 | int ret; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2017 | |
Thomas Gleixner | cd68998 | 2008-02-01 17:45:14 +0100 | [diff] [blame] | 2018 | if (!bitset) |
| 2019 | return -EINVAL; |
Thomas Gleixner | cd68998 | 2008-02-01 17:45:14 +0100 | [diff] [blame] | 2020 | q.bitset = bitset; |
Darren Hart | ca5f952 | 2009-04-03 13:39:33 -0700 | [diff] [blame] | 2021 | |
| 2022 | if (abs_time) { |
| 2023 | to = &timeout; |
| 2024 | |
Darren Hart | b41277d | 2010-11-08 13:10:09 -0800 | [diff] [blame] | 2025 | hrtimer_init_on_stack(&to->timer, (flags & FLAGS_CLOCKRT) ? |
| 2026 | CLOCK_REALTIME : CLOCK_MONOTONIC, |
| 2027 | HRTIMER_MODE_ABS); |
Darren Hart | ca5f952 | 2009-04-03 13:39:33 -0700 | [diff] [blame] | 2028 | hrtimer_init_sleeper(to, current); |
| 2029 | hrtimer_set_expires_range_ns(&to->timer, *abs_time, |
| 2030 | current->timer_slack_ns); |
| 2031 | } |
| 2032 | |
Thomas Gleixner | d58e657 | 2009-10-13 20:40:43 +0200 | [diff] [blame] | 2033 | retry: |
Darren Hart | 7ada876 | 2010-10-17 08:35:04 -0700 | [diff] [blame] | 2034 | /* |
| 2035 | * Prepare to wait on uaddr. On success, holds hb lock and increments |
| 2036 | * q.key refs. |
| 2037 | */ |
Darren Hart | b41277d | 2010-11-08 13:10:09 -0800 | [diff] [blame] | 2038 | ret = futex_wait_setup(uaddr, val, flags, &q, &hb); |
Darren Hart | f801073 | 2009-04-03 13:40:40 -0700 | [diff] [blame] | 2039 | if (ret) |
Darren Hart | 42d35d4 | 2008-12-29 15:49:53 -0800 | [diff] [blame] | 2040 | goto out; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2041 | |
Darren Hart | ca5f952 | 2009-04-03 13:39:33 -0700 | [diff] [blame] | 2042 | /* queue_me and wait for wakeup, timeout, or a signal. */ |
Thomas Gleixner | f1a11e0 | 2009-05-05 19:21:40 +0200 | [diff] [blame] | 2043 | futex_wait_queue_me(hb, &q, to); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2044 | |
| 2045 | /* If we were woken (and unqueued), we succeeded, whatever. */ |
Peter Zijlstra | 2fff78c | 2009-02-11 18:10:10 +0100 | [diff] [blame] | 2046 | ret = 0; |
Darren Hart | 7ada876 | 2010-10-17 08:35:04 -0700 | [diff] [blame] | 2047 | /* unqueue_me() drops q.key ref */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2048 | if (!unqueue_me(&q)) |
Darren Hart | 7ada876 | 2010-10-17 08:35:04 -0700 | [diff] [blame] | 2049 | goto out; |
Peter Zijlstra | 2fff78c | 2009-02-11 18:10:10 +0100 | [diff] [blame] | 2050 | ret = -ETIMEDOUT; |
Darren Hart | ca5f952 | 2009-04-03 13:39:33 -0700 | [diff] [blame] | 2051 | if (to && !to->task) |
Darren Hart | 7ada876 | 2010-10-17 08:35:04 -0700 | [diff] [blame] | 2052 | goto out; |
Nick Piggin | 72c1bbf | 2007-05-08 00:26:43 -0700 | [diff] [blame] | 2053 | |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 2054 | /* |
Thomas Gleixner | d58e657 | 2009-10-13 20:40:43 +0200 | [diff] [blame] | 2055 | * We expect signal_pending(current), but we might be the |
| 2056 | * victim of a spurious wakeup as well. |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 2057 | */ |
Darren Hart | 7ada876 | 2010-10-17 08:35:04 -0700 | [diff] [blame] | 2058 | if (!signal_pending(current)) |
Thomas Gleixner | d58e657 | 2009-10-13 20:40:43 +0200 | [diff] [blame] | 2059 | goto retry; |
Thomas Gleixner | d58e657 | 2009-10-13 20:40:43 +0200 | [diff] [blame] | 2060 | |
Peter Zijlstra | 2fff78c | 2009-02-11 18:10:10 +0100 | [diff] [blame] | 2061 | ret = -ERESTARTSYS; |
Pierre Peiffer | c19384b | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 2062 | if (!abs_time) |
Darren Hart | 7ada876 | 2010-10-17 08:35:04 -0700 | [diff] [blame] | 2063 | goto out; |
Steven Rostedt | ce6bd42 | 2007-12-05 15:46:09 +0100 | [diff] [blame] | 2064 | |
Peter Zijlstra | 2fff78c | 2009-02-11 18:10:10 +0100 | [diff] [blame] | 2065 | restart = ¤t_thread_info()->restart_block; |
| 2066 | restart->fn = futex_wait_restart; |
Namhyung Kim | a3c74c5 | 2010-09-14 21:43:47 +0900 | [diff] [blame] | 2067 | restart->futex.uaddr = uaddr; |
Peter Zijlstra | 2fff78c | 2009-02-11 18:10:10 +0100 | [diff] [blame] | 2068 | restart->futex.val = val; |
| 2069 | restart->futex.time = abs_time->tv64; |
| 2070 | restart->futex.bitset = bitset; |
Darren Hart | 0cd9c64 | 2011-04-14 15:41:57 -0700 | [diff] [blame] | 2071 | restart->futex.flags = flags | FLAGS_HAS_TIMEOUT; |
Peter Zijlstra | 2fff78c | 2009-02-11 18:10:10 +0100 | [diff] [blame] | 2072 | |
| 2073 | ret = -ERESTART_RESTARTBLOCK; |
| 2074 | |
Darren Hart | 42d35d4 | 2008-12-29 15:49:53 -0800 | [diff] [blame] | 2075 | out: |
Darren Hart | ca5f952 | 2009-04-03 13:39:33 -0700 | [diff] [blame] | 2076 | if (to) { |
| 2077 | hrtimer_cancel(&to->timer); |
| 2078 | destroy_hrtimer_on_stack(&to->timer); |
| 2079 | } |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2080 | return ret; |
| 2081 | } |
| 2082 | |
Nick Piggin | 72c1bbf | 2007-05-08 00:26:43 -0700 | [diff] [blame] | 2083 | |
| 2084 | static long futex_wait_restart(struct restart_block *restart) |
| 2085 | { |
Namhyung Kim | a3c74c5 | 2010-09-14 21:43:47 +0900 | [diff] [blame] | 2086 | u32 __user *uaddr = restart->futex.uaddr; |
Darren Hart | a72188d | 2009-04-03 13:40:22 -0700 | [diff] [blame] | 2087 | ktime_t t, *tp = NULL; |
Nick Piggin | 72c1bbf | 2007-05-08 00:26:43 -0700 | [diff] [blame] | 2088 | |
Darren Hart | a72188d | 2009-04-03 13:40:22 -0700 | [diff] [blame] | 2089 | if (restart->futex.flags & FLAGS_HAS_TIMEOUT) { |
| 2090 | t.tv64 = restart->futex.time; |
| 2091 | tp = &t; |
| 2092 | } |
Nick Piggin | 72c1bbf | 2007-05-08 00:26:43 -0700 | [diff] [blame] | 2093 | restart->fn = do_no_restart_syscall; |
Darren Hart | b41277d | 2010-11-08 13:10:09 -0800 | [diff] [blame] | 2094 | |
| 2095 | return (long)futex_wait(uaddr, restart->futex.flags, |
| 2096 | restart->futex.val, tp, restart->futex.bitset); |
Nick Piggin | 72c1bbf | 2007-05-08 00:26:43 -0700 | [diff] [blame] | 2097 | } |
| 2098 | |
| 2099 | |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2100 | /* |
| 2101 | * Userspace tried a 0 -> TID atomic transition of the futex value |
| 2102 | * and failed. The kernel side here does the whole locking operation: |
| 2103 | * if there are waiters then it will block, it does PI, etc. (Due to |
| 2104 | * races the kernel might see a 0 value of the futex too.) |
| 2105 | */ |
Darren Hart | b41277d | 2010-11-08 13:10:09 -0800 | [diff] [blame] | 2106 | static int futex_lock_pi(u32 __user *uaddr, unsigned int flags, int detect, |
| 2107 | ktime_t *time, int trylock) |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2108 | { |
Thomas Gleixner | c5780e9 | 2006-09-08 09:47:15 -0700 | [diff] [blame] | 2109 | struct hrtimer_sleeper timeout, *to = NULL; |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2110 | struct futex_hash_bucket *hb; |
Darren Hart | 5bdb05f | 2010-11-08 13:40:28 -0800 | [diff] [blame] | 2111 | struct futex_q q = futex_q_init; |
Darren Hart | dd97399 | 2009-04-03 13:40:02 -0700 | [diff] [blame] | 2112 | int res, ret; |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2113 | |
| 2114 | if (refill_pi_state_cache()) |
| 2115 | return -ENOMEM; |
| 2116 | |
Pierre Peiffer | c19384b | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 2117 | if (time) { |
Thomas Gleixner | c5780e9 | 2006-09-08 09:47:15 -0700 | [diff] [blame] | 2118 | to = &timeout; |
Thomas Gleixner | 237fc6e | 2008-04-30 00:55:04 -0700 | [diff] [blame] | 2119 | hrtimer_init_on_stack(&to->timer, CLOCK_REALTIME, |
| 2120 | HRTIMER_MODE_ABS); |
Thomas Gleixner | c5780e9 | 2006-09-08 09:47:15 -0700 | [diff] [blame] | 2121 | hrtimer_init_sleeper(to, current); |
Arjan van de Ven | cc584b2 | 2008-09-01 15:02:30 -0700 | [diff] [blame] | 2122 | hrtimer_set_expires(&to->timer, *time); |
Thomas Gleixner | c5780e9 | 2006-09-08 09:47:15 -0700 | [diff] [blame] | 2123 | } |
| 2124 | |
Darren Hart | 42d35d4 | 2008-12-29 15:49:53 -0800 | [diff] [blame] | 2125 | retry: |
Shawn Bohrer | 9ea7150 | 2011-06-30 11:21:32 -0500 | [diff] [blame] | 2126 | ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &q.key, VERIFY_WRITE); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2127 | if (unlikely(ret != 0)) |
Darren Hart | 42d35d4 | 2008-12-29 15:49:53 -0800 | [diff] [blame] | 2128 | goto out; |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2129 | |
Darren Hart | e4dc5b7 | 2009-03-12 00:56:13 -0700 | [diff] [blame] | 2130 | retry_private: |
Eric Sesterhenn | 82af7ac | 2008-01-25 10:40:46 +0100 | [diff] [blame] | 2131 | hb = queue_lock(&q); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2132 | |
Darren Hart | bab5bc9 | 2009-04-07 23:23:50 -0700 | [diff] [blame] | 2133 | ret = futex_lock_pi_atomic(uaddr, hb, &q.key, &q.pi_state, current, 0); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2134 | if (unlikely(ret)) { |
Alexey Kuznetsov | 778e9a9 | 2007-06-08 13:47:00 -0700 | [diff] [blame] | 2135 | switch (ret) { |
Darren Hart | 1a52084 | 2009-04-03 13:39:52 -0700 | [diff] [blame] | 2136 | case 1: |
| 2137 | /* We got the lock. */ |
| 2138 | ret = 0; |
| 2139 | goto out_unlock_put_key; |
| 2140 | case -EFAULT: |
| 2141 | goto uaddr_faulted; |
Alexey Kuznetsov | 778e9a9 | 2007-06-08 13:47:00 -0700 | [diff] [blame] | 2142 | case -EAGAIN: |
| 2143 | /* |
| 2144 | * Task is exiting and we just wait for the |
| 2145 | * exit to complete. |
| 2146 | */ |
Jason Low | 0d00c7b | 2014-01-12 15:31:22 -0800 | [diff] [blame] | 2147 | queue_unlock(hb); |
Thomas Gleixner | ae791a2 | 2010-11-10 13:30:36 +0100 | [diff] [blame] | 2148 | put_futex_key(&q.key); |
Alexey Kuznetsov | 778e9a9 | 2007-06-08 13:47:00 -0700 | [diff] [blame] | 2149 | cond_resched(); |
| 2150 | goto retry; |
Alexey Kuznetsov | 778e9a9 | 2007-06-08 13:47:00 -0700 | [diff] [blame] | 2151 | default: |
Darren Hart | 42d35d4 | 2008-12-29 15:49:53 -0800 | [diff] [blame] | 2152 | goto out_unlock_put_key; |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2153 | } |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2154 | } |
| 2155 | |
| 2156 | /* |
| 2157 | * Only actually queue now that the atomic ops are done: |
| 2158 | */ |
Eric Sesterhenn | 82af7ac | 2008-01-25 10:40:46 +0100 | [diff] [blame] | 2159 | queue_me(&q, hb); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2160 | |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2161 | WARN_ON(!q.pi_state); |
| 2162 | /* |
| 2163 | * Block on the PI mutex: |
| 2164 | */ |
| 2165 | if (!trylock) |
| 2166 | ret = rt_mutex_timed_lock(&q.pi_state->pi_mutex, to, 1); |
| 2167 | else { |
| 2168 | ret = rt_mutex_trylock(&q.pi_state->pi_mutex); |
| 2169 | /* Fixup the trylock return value: */ |
| 2170 | ret = ret ? 0 : -EWOULDBLOCK; |
| 2171 | } |
| 2172 | |
Vernon Mauery | a99e4e4 | 2006-07-01 04:35:42 -0700 | [diff] [blame] | 2173 | spin_lock(q.lock_ptr); |
Darren Hart | dd97399 | 2009-04-03 13:40:02 -0700 | [diff] [blame] | 2174 | /* |
| 2175 | * Fixup the pi_state owner and possibly acquire the lock if we |
| 2176 | * haven't already. |
| 2177 | */ |
Thomas Gleixner | ae791a2 | 2010-11-10 13:30:36 +0100 | [diff] [blame] | 2178 | res = fixup_owner(uaddr, &q, !ret); |
Darren Hart | dd97399 | 2009-04-03 13:40:02 -0700 | [diff] [blame] | 2179 | /* |
| 2180 | * If fixup_owner() returned an error, proprogate that. If it acquired |
| 2181 | * the lock, clear our -ETIMEDOUT or -EINTR. |
| 2182 | */ |
| 2183 | if (res) |
| 2184 | ret = (res < 0) ? res : 0; |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2185 | |
Darren Hart | e8f6386 | 2009-03-12 00:56:06 -0700 | [diff] [blame] | 2186 | /* |
Darren Hart | dd97399 | 2009-04-03 13:40:02 -0700 | [diff] [blame] | 2187 | * If fixup_owner() faulted and was unable to handle the fault, unlock |
| 2188 | * it and return the fault to userspace. |
Darren Hart | e8f6386 | 2009-03-12 00:56:06 -0700 | [diff] [blame] | 2189 | */ |
| 2190 | if (ret && (rt_mutex_owner(&q.pi_state->pi_mutex) == current)) |
| 2191 | rt_mutex_unlock(&q.pi_state->pi_mutex); |
| 2192 | |
Alexey Kuznetsov | 778e9a9 | 2007-06-08 13:47:00 -0700 | [diff] [blame] | 2193 | /* Unqueue and drop the lock */ |
| 2194 | unqueue_me_pi(&q); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2195 | |
Mikael Pettersson | 5ecb01c | 2010-01-23 22:36:29 +0100 | [diff] [blame] | 2196 | goto out_put_key; |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2197 | |
Darren Hart | 42d35d4 | 2008-12-29 15:49:53 -0800 | [diff] [blame] | 2198 | out_unlock_put_key: |
Jason Low | 0d00c7b | 2014-01-12 15:31:22 -0800 | [diff] [blame] | 2199 | queue_unlock(hb); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2200 | |
Darren Hart | 42d35d4 | 2008-12-29 15:49:53 -0800 | [diff] [blame] | 2201 | out_put_key: |
Thomas Gleixner | ae791a2 | 2010-11-10 13:30:36 +0100 | [diff] [blame] | 2202 | put_futex_key(&q.key); |
Darren Hart | 42d35d4 | 2008-12-29 15:49:53 -0800 | [diff] [blame] | 2203 | out: |
Thomas Gleixner | 237fc6e | 2008-04-30 00:55:04 -0700 | [diff] [blame] | 2204 | if (to) |
| 2205 | destroy_hrtimer_on_stack(&to->timer); |
Darren Hart | dd97399 | 2009-04-03 13:40:02 -0700 | [diff] [blame] | 2206 | return ret != -EINTR ? ret : -ERESTARTNOINTR; |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2207 | |
Darren Hart | 42d35d4 | 2008-12-29 15:49:53 -0800 | [diff] [blame] | 2208 | uaddr_faulted: |
Jason Low | 0d00c7b | 2014-01-12 15:31:22 -0800 | [diff] [blame] | 2209 | queue_unlock(hb); |
Alexey Kuznetsov | 778e9a9 | 2007-06-08 13:47:00 -0700 | [diff] [blame] | 2210 | |
Thomas Gleixner | d072599 | 2009-06-11 23:15:43 +0200 | [diff] [blame] | 2211 | ret = fault_in_user_writeable(uaddr); |
Darren Hart | e4dc5b7 | 2009-03-12 00:56:13 -0700 | [diff] [blame] | 2212 | if (ret) |
| 2213 | goto out_put_key; |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2214 | |
Darren Hart | b41277d | 2010-11-08 13:10:09 -0800 | [diff] [blame] | 2215 | if (!(flags & FLAGS_SHARED)) |
Darren Hart | e4dc5b7 | 2009-03-12 00:56:13 -0700 | [diff] [blame] | 2216 | goto retry_private; |
| 2217 | |
Thomas Gleixner | ae791a2 | 2010-11-10 13:30:36 +0100 | [diff] [blame] | 2218 | put_futex_key(&q.key); |
Darren Hart | e4dc5b7 | 2009-03-12 00:56:13 -0700 | [diff] [blame] | 2219 | goto retry; |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2220 | } |
| 2221 | |
| 2222 | /* |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2223 | * Userspace attempted a TID -> 0 atomic transition, and failed. |
| 2224 | * This is the in-kernel slowpath: we look up the PI state (if any), |
| 2225 | * and do the rt-mutex unlock. |
| 2226 | */ |
Darren Hart | b41277d | 2010-11-08 13:10:09 -0800 | [diff] [blame] | 2227 | static int futex_unlock_pi(u32 __user *uaddr, unsigned int flags) |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2228 | { |
| 2229 | struct futex_hash_bucket *hb; |
| 2230 | struct futex_q *this, *next; |
Peter Zijlstra | 38d47c1 | 2008-09-26 19:32:20 +0200 | [diff] [blame] | 2231 | union futex_key key = FUTEX_KEY_INIT; |
Thomas Gleixner | c0c9ed1 | 2011-03-11 11:51:22 +0100 | [diff] [blame] | 2232 | u32 uval, vpid = task_pid_vnr(current); |
Darren Hart | e4dc5b7 | 2009-03-12 00:56:13 -0700 | [diff] [blame] | 2233 | int ret; |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2234 | |
| 2235 | retry: |
| 2236 | if (get_user(uval, uaddr)) |
| 2237 | return -EFAULT; |
| 2238 | /* |
| 2239 | * We release only a lock we actually own: |
| 2240 | */ |
Thomas Gleixner | c0c9ed1 | 2011-03-11 11:51:22 +0100 | [diff] [blame] | 2241 | if ((uval & FUTEX_TID_MASK) != vpid) |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2242 | return -EPERM; |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2243 | |
Shawn Bohrer | 9ea7150 | 2011-06-30 11:21:32 -0500 | [diff] [blame] | 2244 | ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &key, VERIFY_WRITE); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2245 | if (unlikely(ret != 0)) |
| 2246 | goto out; |
| 2247 | |
| 2248 | hb = hash_futex(&key); |
| 2249 | spin_lock(&hb->lock); |
| 2250 | |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2251 | /* |
| 2252 | * To avoid races, try to do the TID -> 0 atomic transition |
| 2253 | * again. If it succeeds then we can return without waking |
| 2254 | * anyone else up: |
| 2255 | */ |
Michel Lespinasse | 37a9d91 | 2011-03-10 18:48:51 -0800 | [diff] [blame] | 2256 | if (!(uval & FUTEX_OWNER_DIED) && |
| 2257 | cmpxchg_futex_value_locked(&uval, uaddr, vpid, 0)) |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2258 | goto pi_faulted; |
| 2259 | /* |
| 2260 | * Rare case: we managed to release the lock atomically, |
| 2261 | * no need to wake anyone else up: |
| 2262 | */ |
Thomas Gleixner | c0c9ed1 | 2011-03-11 11:51:22 +0100 | [diff] [blame] | 2263 | if (unlikely(uval == vpid)) |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2264 | goto out_unlock; |
| 2265 | |
| 2266 | /* |
| 2267 | * Ok, other tasks may need to be woken up - check waiters |
| 2268 | * and do the wakeup if necessary: |
| 2269 | */ |
Jason Low | 0d00c7b | 2014-01-12 15:31:22 -0800 | [diff] [blame] | 2270 | plist_for_each_entry_safe(this, next, &hb->chain, list) { |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2271 | if (!match_futex (&this->key, &key)) |
| 2272 | continue; |
| 2273 | ret = wake_futex_pi(uaddr, uval, this); |
| 2274 | /* |
| 2275 | * The atomic access to the futex value |
| 2276 | * generated a pagefault, so retry the |
| 2277 | * user-access and the wakeup: |
| 2278 | */ |
| 2279 | if (ret == -EFAULT) |
| 2280 | goto pi_faulted; |
| 2281 | goto out_unlock; |
| 2282 | } |
| 2283 | /* |
| 2284 | * No waiters - kernel unlocks the futex: |
| 2285 | */ |
Ingo Molnar | e3f2dde | 2006-07-29 05:17:57 +0200 | [diff] [blame] | 2286 | if (!(uval & FUTEX_OWNER_DIED)) { |
| 2287 | ret = unlock_futex_pi(uaddr, uval); |
| 2288 | if (ret == -EFAULT) |
| 2289 | goto pi_faulted; |
| 2290 | } |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2291 | |
| 2292 | out_unlock: |
| 2293 | spin_unlock(&hb->lock); |
Thomas Gleixner | ae791a2 | 2010-11-10 13:30:36 +0100 | [diff] [blame] | 2294 | put_futex_key(&key); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2295 | |
Darren Hart | 42d35d4 | 2008-12-29 15:49:53 -0800 | [diff] [blame] | 2296 | out: |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2297 | return ret; |
| 2298 | |
| 2299 | pi_faulted: |
Alexey Kuznetsov | 778e9a9 | 2007-06-08 13:47:00 -0700 | [diff] [blame] | 2300 | spin_unlock(&hb->lock); |
Thomas Gleixner | ae791a2 | 2010-11-10 13:30:36 +0100 | [diff] [blame] | 2301 | put_futex_key(&key); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2302 | |
Thomas Gleixner | d072599 | 2009-06-11 23:15:43 +0200 | [diff] [blame] | 2303 | ret = fault_in_user_writeable(uaddr); |
Darren Hart | b568636 | 2008-12-18 15:06:34 -0800 | [diff] [blame] | 2304 | if (!ret) |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2305 | goto retry; |
| 2306 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2307 | return ret; |
| 2308 | } |
| 2309 | |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2310 | /** |
| 2311 | * handle_early_requeue_pi_wakeup() - Detect early wakeup on the initial futex |
| 2312 | * @hb: the hash_bucket futex_q was original enqueued on |
| 2313 | * @q: the futex_q woken while waiting to be requeued |
| 2314 | * @key2: the futex_key of the requeue target futex |
| 2315 | * @timeout: the timeout associated with the wait (NULL if none) |
| 2316 | * |
| 2317 | * Detect if the task was woken on the initial futex as opposed to the requeue |
| 2318 | * target futex. If so, determine if it was a timeout or a signal that caused |
| 2319 | * the wakeup and return the appropriate error code to the caller. Must be |
| 2320 | * called with the hb lock held. |
| 2321 | * |
Randy Dunlap | 6c23cbb | 2013-03-05 10:00:24 -0800 | [diff] [blame] | 2322 | * Return: |
| 2323 | * 0 = no early wakeup detected; |
| 2324 | * <0 = -ETIMEDOUT or -ERESTARTNOINTR |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2325 | */ |
| 2326 | static inline |
| 2327 | int handle_early_requeue_pi_wakeup(struct futex_hash_bucket *hb, |
| 2328 | struct futex_q *q, union futex_key *key2, |
| 2329 | struct hrtimer_sleeper *timeout) |
| 2330 | { |
| 2331 | int ret = 0; |
| 2332 | |
| 2333 | /* |
| 2334 | * With the hb lock held, we avoid races while we process the wakeup. |
| 2335 | * We only need to hold hb (and not hb2) to ensure atomicity as the |
| 2336 | * wakeup code can't change q.key from uaddr to uaddr2 if we hold hb. |
| 2337 | * It can't be requeued from uaddr2 to something else since we don't |
| 2338 | * support a PI aware source futex for requeue. |
| 2339 | */ |
| 2340 | if (!match_futex(&q->key, key2)) { |
| 2341 | WARN_ON(q->lock_ptr && (&hb->lock != q->lock_ptr)); |
| 2342 | /* |
| 2343 | * We were woken prior to requeue by a timeout or a signal. |
| 2344 | * Unqueue the futex_q and determine which it was. |
| 2345 | */ |
Lai Jiangshan | 2e12978 | 2010-12-22 14:18:50 +0800 | [diff] [blame] | 2346 | plist_del(&q->list, &hb->chain); |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2347 | |
Thomas Gleixner | d58e657 | 2009-10-13 20:40:43 +0200 | [diff] [blame] | 2348 | /* Handle spurious wakeups gracefully */ |
Thomas Gleixner | 11df6dd | 2009-10-28 20:26:48 +0100 | [diff] [blame] | 2349 | ret = -EWOULDBLOCK; |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2350 | if (timeout && !timeout->task) |
| 2351 | ret = -ETIMEDOUT; |
Thomas Gleixner | d58e657 | 2009-10-13 20:40:43 +0200 | [diff] [blame] | 2352 | else if (signal_pending(current)) |
Thomas Gleixner | 1c840c1 | 2009-05-20 09:22:40 +0200 | [diff] [blame] | 2353 | ret = -ERESTARTNOINTR; |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2354 | } |
| 2355 | return ret; |
| 2356 | } |
| 2357 | |
| 2358 | /** |
| 2359 | * futex_wait_requeue_pi() - Wait on uaddr and take uaddr2 |
Darren Hart | 56ec160 | 2009-09-21 22:29:59 -0700 | [diff] [blame] | 2360 | * @uaddr: the futex we initially wait on (non-pi) |
Darren Hart | b41277d | 2010-11-08 13:10:09 -0800 | [diff] [blame] | 2361 | * @flags: futex flags (FLAGS_SHARED, FLAGS_CLOCKRT, etc.), they must be |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2362 | * the same type, no requeueing from private to shared, etc. |
| 2363 | * @val: the expected value of uaddr |
| 2364 | * @abs_time: absolute timeout |
Darren Hart | 56ec160 | 2009-09-21 22:29:59 -0700 | [diff] [blame] | 2365 | * @bitset: 32 bit wakeup bitset set by userspace, defaults to all |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2366 | * @uaddr2: the pi futex we will take prior to returning to user-space |
| 2367 | * |
| 2368 | * The caller will wait on uaddr and will be requeued by futex_requeue() to |
Darren Hart | 6f7b0a2 | 2012-07-20 11:53:31 -0700 | [diff] [blame] | 2369 | * uaddr2 which must be PI aware and unique from uaddr. Normal wakeup will wake |
| 2370 | * on uaddr2 and complete the acquisition of the rt_mutex prior to returning to |
| 2371 | * userspace. This ensures the rt_mutex maintains an owner when it has waiters; |
| 2372 | * without one, the pi logic would not know which task to boost/deboost, if |
| 2373 | * there was a need to. |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2374 | * |
| 2375 | * We call schedule in futex_wait_queue_me() when we enqueue and return there |
Randy Dunlap | 6c23cbb | 2013-03-05 10:00:24 -0800 | [diff] [blame] | 2376 | * via the following-- |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2377 | * 1) wakeup on uaddr2 after an atomic lock acquisition by futex_requeue() |
Darren Hart | cc6db4e | 2009-07-31 16:20:10 -0700 | [diff] [blame] | 2378 | * 2) wakeup on uaddr2 after a requeue |
| 2379 | * 3) signal |
| 2380 | * 4) timeout |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2381 | * |
Darren Hart | cc6db4e | 2009-07-31 16:20:10 -0700 | [diff] [blame] | 2382 | * If 3, cleanup and return -ERESTARTNOINTR. |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2383 | * |
| 2384 | * If 2, we may then block on trying to take the rt_mutex and return via: |
| 2385 | * 5) successful lock |
| 2386 | * 6) signal |
| 2387 | * 7) timeout |
| 2388 | * 8) other lock acquisition failure |
| 2389 | * |
Darren Hart | cc6db4e | 2009-07-31 16:20:10 -0700 | [diff] [blame] | 2390 | * If 6, return -EWOULDBLOCK (restarting the syscall would do the same). |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2391 | * |
| 2392 | * If 4 or 7, we cleanup and return with -ETIMEDOUT. |
| 2393 | * |
Randy Dunlap | 6c23cbb | 2013-03-05 10:00:24 -0800 | [diff] [blame] | 2394 | * Return: |
| 2395 | * 0 - On success; |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2396 | * <0 - On error |
| 2397 | */ |
Darren Hart | b41277d | 2010-11-08 13:10:09 -0800 | [diff] [blame] | 2398 | static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags, |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2399 | u32 val, ktime_t *abs_time, u32 bitset, |
Darren Hart | b41277d | 2010-11-08 13:10:09 -0800 | [diff] [blame] | 2400 | u32 __user *uaddr2) |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2401 | { |
| 2402 | struct hrtimer_sleeper timeout, *to = NULL; |
| 2403 | struct rt_mutex_waiter rt_waiter; |
| 2404 | struct rt_mutex *pi_mutex = NULL; |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2405 | struct futex_hash_bucket *hb; |
Darren Hart | 5bdb05f | 2010-11-08 13:40:28 -0800 | [diff] [blame] | 2406 | union futex_key key2 = FUTEX_KEY_INIT; |
| 2407 | struct futex_q q = futex_q_init; |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2408 | int res, ret; |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2409 | |
Darren Hart | 6f7b0a2 | 2012-07-20 11:53:31 -0700 | [diff] [blame] | 2410 | if (uaddr == uaddr2) |
| 2411 | return -EINVAL; |
| 2412 | |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2413 | if (!bitset) |
| 2414 | return -EINVAL; |
| 2415 | |
| 2416 | if (abs_time) { |
| 2417 | to = &timeout; |
Darren Hart | b41277d | 2010-11-08 13:10:09 -0800 | [diff] [blame] | 2418 | hrtimer_init_on_stack(&to->timer, (flags & FLAGS_CLOCKRT) ? |
| 2419 | CLOCK_REALTIME : CLOCK_MONOTONIC, |
| 2420 | HRTIMER_MODE_ABS); |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2421 | hrtimer_init_sleeper(to, current); |
| 2422 | hrtimer_set_expires_range_ns(&to->timer, *abs_time, |
| 2423 | current->timer_slack_ns); |
| 2424 | } |
| 2425 | |
| 2426 | /* |
| 2427 | * The waiter is allocated on our stack, manipulated by the requeue |
| 2428 | * code while we sleep on uaddr. |
| 2429 | */ |
| 2430 | debug_rt_mutex_init_waiter(&rt_waiter); |
Peter Zijlstra | fb00aca | 2013-11-07 14:43:43 +0100 | [diff] [blame] | 2431 | RB_CLEAR_NODE(&rt_waiter.pi_tree_entry); |
| 2432 | RB_CLEAR_NODE(&rt_waiter.tree_entry); |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2433 | rt_waiter.task = NULL; |
| 2434 | |
Shawn Bohrer | 9ea7150 | 2011-06-30 11:21:32 -0500 | [diff] [blame] | 2435 | ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2, VERIFY_WRITE); |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2436 | if (unlikely(ret != 0)) |
| 2437 | goto out; |
| 2438 | |
Darren Hart | 84bc4af | 2009-08-13 17:36:53 -0700 | [diff] [blame] | 2439 | q.bitset = bitset; |
| 2440 | q.rt_waiter = &rt_waiter; |
| 2441 | q.requeue_pi_key = &key2; |
| 2442 | |
Darren Hart | 7ada876 | 2010-10-17 08:35:04 -0700 | [diff] [blame] | 2443 | /* |
| 2444 | * Prepare to wait on uaddr. On success, increments q.key (key1) ref |
| 2445 | * count. |
| 2446 | */ |
Darren Hart | b41277d | 2010-11-08 13:10:09 -0800 | [diff] [blame] | 2447 | ret = futex_wait_setup(uaddr, val, flags, &q, &hb); |
Thomas Gleixner | c8b15a7 | 2009-05-20 09:18:50 +0200 | [diff] [blame] | 2448 | if (ret) |
| 2449 | goto out_key2; |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2450 | |
| 2451 | /* Queue the futex_q, drop the hb lock, wait for wakeup. */ |
Thomas Gleixner | f1a11e0 | 2009-05-05 19:21:40 +0200 | [diff] [blame] | 2452 | futex_wait_queue_me(hb, &q, to); |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2453 | |
| 2454 | spin_lock(&hb->lock); |
| 2455 | ret = handle_early_requeue_pi_wakeup(hb, &q, &key2, to); |
| 2456 | spin_unlock(&hb->lock); |
| 2457 | if (ret) |
| 2458 | goto out_put_keys; |
| 2459 | |
| 2460 | /* |
| 2461 | * In order for us to be here, we know our q.key == key2, and since |
| 2462 | * we took the hb->lock above, we also know that futex_requeue() has |
| 2463 | * completed and we no longer have to concern ourselves with a wakeup |
Darren Hart | 7ada876 | 2010-10-17 08:35:04 -0700 | [diff] [blame] | 2464 | * race with the atomic proxy lock acquisition by the requeue code. The |
| 2465 | * futex_requeue dropped our key1 reference and incremented our key2 |
| 2466 | * reference count. |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2467 | */ |
| 2468 | |
| 2469 | /* Check if the requeue code acquired the second futex for us. */ |
| 2470 | if (!q.rt_waiter) { |
| 2471 | /* |
| 2472 | * Got the lock. We might not be the anticipated owner if we |
| 2473 | * did a lock-steal - fix up the PI-state in that case. |
| 2474 | */ |
| 2475 | if (q.pi_state && (q.pi_state->owner != current)) { |
| 2476 | spin_lock(q.lock_ptr); |
Thomas Gleixner | ae791a2 | 2010-11-10 13:30:36 +0100 | [diff] [blame] | 2477 | ret = fixup_pi_state_owner(uaddr2, &q, current); |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2478 | spin_unlock(q.lock_ptr); |
| 2479 | } |
| 2480 | } else { |
| 2481 | /* |
| 2482 | * We have been woken up by futex_unlock_pi(), a timeout, or a |
| 2483 | * signal. futex_unlock_pi() will not destroy the lock_ptr nor |
| 2484 | * the pi_state. |
| 2485 | */ |
Darren Hart | f27071c | 2012-07-20 11:53:30 -0700 | [diff] [blame] | 2486 | WARN_ON(!q.pi_state); |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2487 | pi_mutex = &q.pi_state->pi_mutex; |
| 2488 | ret = rt_mutex_finish_proxy_lock(pi_mutex, to, &rt_waiter, 1); |
| 2489 | debug_rt_mutex_free_waiter(&rt_waiter); |
| 2490 | |
| 2491 | spin_lock(q.lock_ptr); |
| 2492 | /* |
| 2493 | * Fixup the pi_state owner and possibly acquire the lock if we |
| 2494 | * haven't already. |
| 2495 | */ |
Thomas Gleixner | ae791a2 | 2010-11-10 13:30:36 +0100 | [diff] [blame] | 2496 | res = fixup_owner(uaddr2, &q, !ret); |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2497 | /* |
| 2498 | * If fixup_owner() returned an error, proprogate that. If it |
Darren Hart | 56ec160 | 2009-09-21 22:29:59 -0700 | [diff] [blame] | 2499 | * acquired the lock, clear -ETIMEDOUT or -EINTR. |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2500 | */ |
| 2501 | if (res) |
| 2502 | ret = (res < 0) ? res : 0; |
| 2503 | |
| 2504 | /* Unqueue and drop the lock. */ |
| 2505 | unqueue_me_pi(&q); |
| 2506 | } |
| 2507 | |
| 2508 | /* |
| 2509 | * If fixup_pi_state_owner() faulted and was unable to handle the |
| 2510 | * fault, unlock the rt_mutex and return the fault to userspace. |
| 2511 | */ |
| 2512 | if (ret == -EFAULT) { |
Darren Hart | b6070a8 | 2012-07-20 11:53:29 -0700 | [diff] [blame] | 2513 | if (pi_mutex && rt_mutex_owner(pi_mutex) == current) |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2514 | rt_mutex_unlock(pi_mutex); |
| 2515 | } else if (ret == -EINTR) { |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2516 | /* |
Darren Hart | cc6db4e | 2009-07-31 16:20:10 -0700 | [diff] [blame] | 2517 | * We've already been requeued, but cannot restart by calling |
| 2518 | * futex_lock_pi() directly. We could restart this syscall, but |
| 2519 | * it would detect that the user space "val" changed and return |
| 2520 | * -EWOULDBLOCK. Save the overhead of the restart and return |
| 2521 | * -EWOULDBLOCK directly. |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2522 | */ |
Thomas Gleixner | 2070887 | 2009-05-19 23:04:59 +0200 | [diff] [blame] | 2523 | ret = -EWOULDBLOCK; |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2524 | } |
| 2525 | |
| 2526 | out_put_keys: |
Thomas Gleixner | ae791a2 | 2010-11-10 13:30:36 +0100 | [diff] [blame] | 2527 | put_futex_key(&q.key); |
Thomas Gleixner | c8b15a7 | 2009-05-20 09:18:50 +0200 | [diff] [blame] | 2528 | out_key2: |
Thomas Gleixner | ae791a2 | 2010-11-10 13:30:36 +0100 | [diff] [blame] | 2529 | put_futex_key(&key2); |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2530 | |
| 2531 | out: |
| 2532 | if (to) { |
| 2533 | hrtimer_cancel(&to->timer); |
| 2534 | destroy_hrtimer_on_stack(&to->timer); |
| 2535 | } |
| 2536 | return ret; |
| 2537 | } |
| 2538 | |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2539 | /* |
| 2540 | * Support for robust futexes: the kernel cleans up held futexes at |
| 2541 | * thread exit time. |
| 2542 | * |
| 2543 | * Implementation: user-space maintains a per-thread list of locks it |
| 2544 | * is holding. Upon do_exit(), the kernel carefully walks this list, |
| 2545 | * and marks all locks that are owned by this thread with the |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2546 | * FUTEX_OWNER_DIED bit, and wakes up a waiter (if any). The list is |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2547 | * always manipulated with the lock held, so the list is private and |
| 2548 | * per-thread. Userspace also maintains a per-thread 'list_op_pending' |
| 2549 | * field, to allow the kernel to clean up if the thread dies after |
| 2550 | * acquiring the lock, but just before it could have added itself to |
| 2551 | * the list. There can only be one such pending lock. |
| 2552 | */ |
| 2553 | |
| 2554 | /** |
Darren Hart | d96ee56 | 2009-09-21 22:30:22 -0700 | [diff] [blame] | 2555 | * sys_set_robust_list() - Set the robust-futex list head of a task |
| 2556 | * @head: pointer to the list-head |
| 2557 | * @len: length of the list-head, as userspace expects |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2558 | */ |
Heiko Carstens | 836f92a | 2009-01-14 14:14:33 +0100 | [diff] [blame] | 2559 | SYSCALL_DEFINE2(set_robust_list, struct robust_list_head __user *, head, |
| 2560 | size_t, len) |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2561 | { |
Thomas Gleixner | a0c1e90 | 2008-02-23 15:23:57 -0800 | [diff] [blame] | 2562 | if (!futex_cmpxchg_enabled) |
| 2563 | return -ENOSYS; |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2564 | /* |
| 2565 | * The kernel knows only one size for now: |
| 2566 | */ |
| 2567 | if (unlikely(len != sizeof(*head))) |
| 2568 | return -EINVAL; |
| 2569 | |
| 2570 | current->robust_list = head; |
| 2571 | |
| 2572 | return 0; |
| 2573 | } |
| 2574 | |
| 2575 | /** |
Darren Hart | d96ee56 | 2009-09-21 22:30:22 -0700 | [diff] [blame] | 2576 | * sys_get_robust_list() - Get the robust-futex list head of a task |
| 2577 | * @pid: pid of the process [zero for current task] |
| 2578 | * @head_ptr: pointer to a list-head pointer, the kernel fills it in |
| 2579 | * @len_ptr: pointer to a length field, the kernel fills in the header size |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2580 | */ |
Heiko Carstens | 836f92a | 2009-01-14 14:14:33 +0100 | [diff] [blame] | 2581 | SYSCALL_DEFINE3(get_robust_list, int, pid, |
| 2582 | struct robust_list_head __user * __user *, head_ptr, |
| 2583 | size_t __user *, len_ptr) |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2584 | { |
Al Viro | ba46df9 | 2006-10-10 22:46:07 +0100 | [diff] [blame] | 2585 | struct robust_list_head __user *head; |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2586 | unsigned long ret; |
Kees Cook | bdbb776 | 2012-03-19 16:12:53 -0700 | [diff] [blame] | 2587 | struct task_struct *p; |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2588 | |
Thomas Gleixner | a0c1e90 | 2008-02-23 15:23:57 -0800 | [diff] [blame] | 2589 | if (!futex_cmpxchg_enabled) |
| 2590 | return -ENOSYS; |
| 2591 | |
Kees Cook | bdbb776 | 2012-03-19 16:12:53 -0700 | [diff] [blame] | 2592 | rcu_read_lock(); |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2593 | |
Kees Cook | bdbb776 | 2012-03-19 16:12:53 -0700 | [diff] [blame] | 2594 | ret = -ESRCH; |
| 2595 | if (!pid) |
| 2596 | p = current; |
| 2597 | else { |
Pavel Emelyanov | 228ebcb | 2007-10-18 23:40:16 -0700 | [diff] [blame] | 2598 | p = find_task_by_vpid(pid); |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2599 | if (!p) |
| 2600 | goto err_unlock; |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2601 | } |
| 2602 | |
Kees Cook | bdbb776 | 2012-03-19 16:12:53 -0700 | [diff] [blame] | 2603 | ret = -EPERM; |
| 2604 | if (!ptrace_may_access(p, PTRACE_MODE_READ)) |
| 2605 | goto err_unlock; |
| 2606 | |
| 2607 | head = p->robust_list; |
| 2608 | rcu_read_unlock(); |
| 2609 | |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2610 | if (put_user(sizeof(*head), len_ptr)) |
| 2611 | return -EFAULT; |
| 2612 | return put_user(head, head_ptr); |
| 2613 | |
| 2614 | err_unlock: |
Oleg Nesterov | aaa2a97 | 2006-09-29 02:00:55 -0700 | [diff] [blame] | 2615 | rcu_read_unlock(); |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2616 | |
| 2617 | return ret; |
| 2618 | } |
| 2619 | |
| 2620 | /* |
| 2621 | * Process a futex-list entry, check whether it's owned by the |
| 2622 | * dying task, and do notification if so: |
| 2623 | */ |
Ingo Molnar | e3f2dde | 2006-07-29 05:17:57 +0200 | [diff] [blame] | 2624 | int handle_futex_death(u32 __user *uaddr, struct task_struct *curr, int pi) |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2625 | { |
Vitaliy Ivanov | 7cfdaf3 | 2011-07-07 15:10:31 +0300 | [diff] [blame] | 2626 | u32 uval, uninitialized_var(nval), mval; |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2627 | |
Ingo Molnar | 8f17d3a | 2006-03-27 01:16:27 -0800 | [diff] [blame] | 2628 | retry: |
| 2629 | if (get_user(uval, uaddr)) |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2630 | return -1; |
| 2631 | |
Pavel Emelyanov | b488893 | 2007-10-18 23:40:14 -0700 | [diff] [blame] | 2632 | if ((uval & FUTEX_TID_MASK) == task_pid_vnr(curr)) { |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2633 | /* |
| 2634 | * Ok, this dying thread is truly holding a futex |
| 2635 | * of interest. Set the OWNER_DIED bit atomically |
| 2636 | * via cmpxchg, and if the value had FUTEX_WAITERS |
| 2637 | * set, wake up a waiter (if any). (We have to do a |
| 2638 | * futex_wake() even if OWNER_DIED is already set - |
| 2639 | * to handle the rare but possible case of recursive |
| 2640 | * thread-death.) The rest of the cleanup is done in |
| 2641 | * userspace. |
| 2642 | */ |
Ingo Molnar | e3f2dde | 2006-07-29 05:17:57 +0200 | [diff] [blame] | 2643 | mval = (uval & FUTEX_WAITERS) | FUTEX_OWNER_DIED; |
Thomas Gleixner | 6e0aa9f | 2011-03-14 10:34:35 +0100 | [diff] [blame] | 2644 | /* |
| 2645 | * We are not holding a lock here, but we want to have |
| 2646 | * the pagefault_disable/enable() protection because |
| 2647 | * we want to handle the fault gracefully. If the |
| 2648 | * access fails we try to fault in the futex with R/W |
| 2649 | * verification via get_user_pages. get_user() above |
| 2650 | * does not guarantee R/W access. If that fails we |
| 2651 | * give up and leave the futex locked. |
| 2652 | */ |
| 2653 | if (cmpxchg_futex_value_locked(&nval, uaddr, uval, mval)) { |
| 2654 | if (fault_in_user_writeable(uaddr)) |
| 2655 | return -1; |
| 2656 | goto retry; |
| 2657 | } |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2658 | if (nval != uval) |
Ingo Molnar | 8f17d3a | 2006-03-27 01:16:27 -0800 | [diff] [blame] | 2659 | goto retry; |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2660 | |
Ingo Molnar | e3f2dde | 2006-07-29 05:17:57 +0200 | [diff] [blame] | 2661 | /* |
| 2662 | * Wake robust non-PI futexes here. The wakeup of |
| 2663 | * PI futexes happens in exit_pi_state(): |
| 2664 | */ |
Thomas Gleixner | 36cf3b5 | 2007-07-15 23:41:20 -0700 | [diff] [blame] | 2665 | if (!pi && (uval & FUTEX_WAITERS)) |
Peter Zijlstra | c2f9f20 | 2008-09-26 19:32:23 +0200 | [diff] [blame] | 2666 | futex_wake(uaddr, 1, 1, FUTEX_BITSET_MATCH_ANY); |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2667 | } |
| 2668 | return 0; |
| 2669 | } |
| 2670 | |
| 2671 | /* |
Ingo Molnar | e3f2dde | 2006-07-29 05:17:57 +0200 | [diff] [blame] | 2672 | * Fetch a robust-list pointer. Bit 0 signals PI futexes: |
| 2673 | */ |
| 2674 | static inline int fetch_robust_entry(struct robust_list __user **entry, |
Al Viro | ba46df9 | 2006-10-10 22:46:07 +0100 | [diff] [blame] | 2675 | struct robust_list __user * __user *head, |
Namhyung Kim | 1dcc41b | 2010-09-14 21:43:46 +0900 | [diff] [blame] | 2676 | unsigned int *pi) |
Ingo Molnar | e3f2dde | 2006-07-29 05:17:57 +0200 | [diff] [blame] | 2677 | { |
| 2678 | unsigned long uentry; |
| 2679 | |
Al Viro | ba46df9 | 2006-10-10 22:46:07 +0100 | [diff] [blame] | 2680 | if (get_user(uentry, (unsigned long __user *)head)) |
Ingo Molnar | e3f2dde | 2006-07-29 05:17:57 +0200 | [diff] [blame] | 2681 | return -EFAULT; |
| 2682 | |
Al Viro | ba46df9 | 2006-10-10 22:46:07 +0100 | [diff] [blame] | 2683 | *entry = (void __user *)(uentry & ~1UL); |
Ingo Molnar | e3f2dde | 2006-07-29 05:17:57 +0200 | [diff] [blame] | 2684 | *pi = uentry & 1; |
| 2685 | |
| 2686 | return 0; |
| 2687 | } |
| 2688 | |
| 2689 | /* |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2690 | * Walk curr->robust_list (very carefully, it's a userspace list!) |
| 2691 | * and mark any locks found there dead, and notify any waiters. |
| 2692 | * |
| 2693 | * We silently return on any sign of list-walking problem. |
| 2694 | */ |
| 2695 | void exit_robust_list(struct task_struct *curr) |
| 2696 | { |
| 2697 | struct robust_list_head __user *head = curr->robust_list; |
Martin Schwidefsky | 9f96cb1 | 2007-10-01 01:20:13 -0700 | [diff] [blame] | 2698 | struct robust_list __user *entry, *next_entry, *pending; |
Darren Hart | 4c115e9 | 2010-11-04 15:00:00 -0400 | [diff] [blame] | 2699 | unsigned int limit = ROBUST_LIST_LIMIT, pi, pip; |
| 2700 | unsigned int uninitialized_var(next_pi); |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2701 | unsigned long futex_offset; |
Martin Schwidefsky | 9f96cb1 | 2007-10-01 01:20:13 -0700 | [diff] [blame] | 2702 | int rc; |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2703 | |
Thomas Gleixner | a0c1e90 | 2008-02-23 15:23:57 -0800 | [diff] [blame] | 2704 | if (!futex_cmpxchg_enabled) |
| 2705 | return; |
| 2706 | |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2707 | /* |
| 2708 | * Fetch the list head (which was registered earlier, via |
| 2709 | * sys_set_robust_list()): |
| 2710 | */ |
Ingo Molnar | e3f2dde | 2006-07-29 05:17:57 +0200 | [diff] [blame] | 2711 | if (fetch_robust_entry(&entry, &head->list.next, &pi)) |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2712 | return; |
| 2713 | /* |
| 2714 | * Fetch the relative futex offset: |
| 2715 | */ |
| 2716 | if (get_user(futex_offset, &head->futex_offset)) |
| 2717 | return; |
| 2718 | /* |
| 2719 | * Fetch any possibly pending lock-add first, and handle it |
| 2720 | * if it exists: |
| 2721 | */ |
Ingo Molnar | e3f2dde | 2006-07-29 05:17:57 +0200 | [diff] [blame] | 2722 | if (fetch_robust_entry(&pending, &head->list_op_pending, &pip)) |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2723 | return; |
Ingo Molnar | e3f2dde | 2006-07-29 05:17:57 +0200 | [diff] [blame] | 2724 | |
Martin Schwidefsky | 9f96cb1 | 2007-10-01 01:20:13 -0700 | [diff] [blame] | 2725 | next_entry = NULL; /* avoid warning with gcc */ |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2726 | while (entry != &head->list) { |
| 2727 | /* |
Martin Schwidefsky | 9f96cb1 | 2007-10-01 01:20:13 -0700 | [diff] [blame] | 2728 | * Fetch the next entry in the list before calling |
| 2729 | * handle_futex_death: |
| 2730 | */ |
| 2731 | rc = fetch_robust_entry(&next_entry, &entry->next, &next_pi); |
| 2732 | /* |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2733 | * A pending lock might already be on the list, so |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2734 | * don't process it twice: |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2735 | */ |
| 2736 | if (entry != pending) |
Al Viro | ba46df9 | 2006-10-10 22:46:07 +0100 | [diff] [blame] | 2737 | if (handle_futex_death((void __user *)entry + futex_offset, |
Ingo Molnar | e3f2dde | 2006-07-29 05:17:57 +0200 | [diff] [blame] | 2738 | curr, pi)) |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2739 | return; |
Martin Schwidefsky | 9f96cb1 | 2007-10-01 01:20:13 -0700 | [diff] [blame] | 2740 | if (rc) |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2741 | return; |
Martin Schwidefsky | 9f96cb1 | 2007-10-01 01:20:13 -0700 | [diff] [blame] | 2742 | entry = next_entry; |
| 2743 | pi = next_pi; |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2744 | /* |
| 2745 | * Avoid excessively long or circular lists: |
| 2746 | */ |
| 2747 | if (!--limit) |
| 2748 | break; |
| 2749 | |
| 2750 | cond_resched(); |
| 2751 | } |
Martin Schwidefsky | 9f96cb1 | 2007-10-01 01:20:13 -0700 | [diff] [blame] | 2752 | |
| 2753 | if (pending) |
| 2754 | handle_futex_death((void __user *)pending + futex_offset, |
| 2755 | curr, pip); |
Ingo Molnar | 0771dfe | 2006-03-27 01:16:22 -0800 | [diff] [blame] | 2756 | } |
| 2757 | |
Pierre Peiffer | c19384b | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 2758 | long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout, |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 2759 | u32 __user *uaddr2, u32 val2, u32 val3) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2760 | { |
Thomas Gleixner | 81b4053 | 2012-02-15 12:17:09 +0100 | [diff] [blame] | 2761 | int cmd = op & FUTEX_CMD_MASK; |
Darren Hart | b41277d | 2010-11-08 13:10:09 -0800 | [diff] [blame] | 2762 | unsigned int flags = 0; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2763 | |
Eric Dumazet | 34f01cc | 2007-05-09 02:35:04 -0700 | [diff] [blame] | 2764 | if (!(op & FUTEX_PRIVATE_FLAG)) |
Darren Hart | b41277d | 2010-11-08 13:10:09 -0800 | [diff] [blame] | 2765 | flags |= FLAGS_SHARED; |
Eric Dumazet | 34f01cc | 2007-05-09 02:35:04 -0700 | [diff] [blame] | 2766 | |
Darren Hart | b41277d | 2010-11-08 13:10:09 -0800 | [diff] [blame] | 2767 | if (op & FUTEX_CLOCK_REALTIME) { |
| 2768 | flags |= FLAGS_CLOCKRT; |
| 2769 | if (cmd != FUTEX_WAIT_BITSET && cmd != FUTEX_WAIT_REQUEUE_PI) |
| 2770 | return -ENOSYS; |
| 2771 | } |
Eric Dumazet | 34f01cc | 2007-05-09 02:35:04 -0700 | [diff] [blame] | 2772 | |
| 2773 | switch (cmd) { |
Thomas Gleixner | 59263b5 | 2012-02-15 12:08:34 +0100 | [diff] [blame] | 2774 | case FUTEX_LOCK_PI: |
| 2775 | case FUTEX_UNLOCK_PI: |
| 2776 | case FUTEX_TRYLOCK_PI: |
| 2777 | case FUTEX_WAIT_REQUEUE_PI: |
| 2778 | case FUTEX_CMP_REQUEUE_PI: |
| 2779 | if (!futex_cmpxchg_enabled) |
| 2780 | return -ENOSYS; |
| 2781 | } |
| 2782 | |
| 2783 | switch (cmd) { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2784 | case FUTEX_WAIT: |
Thomas Gleixner | cd68998 | 2008-02-01 17:45:14 +0100 | [diff] [blame] | 2785 | val3 = FUTEX_BITSET_MATCH_ANY; |
| 2786 | case FUTEX_WAIT_BITSET: |
Thomas Gleixner | 81b4053 | 2012-02-15 12:17:09 +0100 | [diff] [blame] | 2787 | return futex_wait(uaddr, flags, val, timeout, val3); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2788 | case FUTEX_WAKE: |
Thomas Gleixner | cd68998 | 2008-02-01 17:45:14 +0100 | [diff] [blame] | 2789 | val3 = FUTEX_BITSET_MATCH_ANY; |
| 2790 | case FUTEX_WAKE_BITSET: |
Thomas Gleixner | 81b4053 | 2012-02-15 12:17:09 +0100 | [diff] [blame] | 2791 | return futex_wake(uaddr, flags, val, val3); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2792 | case FUTEX_REQUEUE: |
Thomas Gleixner | 81b4053 | 2012-02-15 12:17:09 +0100 | [diff] [blame] | 2793 | return futex_requeue(uaddr, flags, uaddr2, val, val2, NULL, 0); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2794 | case FUTEX_CMP_REQUEUE: |
Thomas Gleixner | 81b4053 | 2012-02-15 12:17:09 +0100 | [diff] [blame] | 2795 | return futex_requeue(uaddr, flags, uaddr2, val, val2, &val3, 0); |
Jakub Jelinek | 4732efb | 2005-09-06 15:16:25 -0700 | [diff] [blame] | 2796 | case FUTEX_WAKE_OP: |
Thomas Gleixner | 81b4053 | 2012-02-15 12:17:09 +0100 | [diff] [blame] | 2797 | return futex_wake_op(uaddr, flags, uaddr2, val, val2, val3); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2798 | case FUTEX_LOCK_PI: |
Thomas Gleixner | 81b4053 | 2012-02-15 12:17:09 +0100 | [diff] [blame] | 2799 | return futex_lock_pi(uaddr, flags, val, timeout, 0); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2800 | case FUTEX_UNLOCK_PI: |
Thomas Gleixner | 81b4053 | 2012-02-15 12:17:09 +0100 | [diff] [blame] | 2801 | return futex_unlock_pi(uaddr, flags); |
Ingo Molnar | c87e283 | 2006-06-27 02:54:58 -0700 | [diff] [blame] | 2802 | case FUTEX_TRYLOCK_PI: |
Thomas Gleixner | 81b4053 | 2012-02-15 12:17:09 +0100 | [diff] [blame] | 2803 | return futex_lock_pi(uaddr, flags, 0, timeout, 1); |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2804 | case FUTEX_WAIT_REQUEUE_PI: |
| 2805 | val3 = FUTEX_BITSET_MATCH_ANY; |
Thomas Gleixner | 81b4053 | 2012-02-15 12:17:09 +0100 | [diff] [blame] | 2806 | return futex_wait_requeue_pi(uaddr, flags, val, timeout, val3, |
| 2807 | uaddr2); |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2808 | case FUTEX_CMP_REQUEUE_PI: |
Thomas Gleixner | 81b4053 | 2012-02-15 12:17:09 +0100 | [diff] [blame] | 2809 | return futex_requeue(uaddr, flags, uaddr2, val, val2, &val3, 1); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2810 | } |
Thomas Gleixner | 81b4053 | 2012-02-15 12:17:09 +0100 | [diff] [blame] | 2811 | return -ENOSYS; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2812 | } |
| 2813 | |
| 2814 | |
Heiko Carstens | 17da2bd | 2009-01-14 14:14:10 +0100 | [diff] [blame] | 2815 | SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val, |
| 2816 | struct timespec __user *, utime, u32 __user *, uaddr2, |
| 2817 | u32, val3) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2818 | { |
Pierre Peiffer | c19384b | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 2819 | struct timespec ts; |
| 2820 | ktime_t t, *tp = NULL; |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 2821 | u32 val2 = 0; |
Eric Dumazet | 34f01cc | 2007-05-09 02:35:04 -0700 | [diff] [blame] | 2822 | int cmd = op & FUTEX_CMD_MASK; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2823 | |
Thomas Gleixner | cd68998 | 2008-02-01 17:45:14 +0100 | [diff] [blame] | 2824 | if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI || |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2825 | cmd == FUTEX_WAIT_BITSET || |
| 2826 | cmd == FUTEX_WAIT_REQUEUE_PI)) { |
Pierre Peiffer | c19384b | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 2827 | if (copy_from_user(&ts, utime, sizeof(ts)) != 0) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2828 | return -EFAULT; |
Pierre Peiffer | c19384b | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 2829 | if (!timespec_valid(&ts)) |
Thomas Gleixner | 9741ef96 | 2006-03-31 02:31:32 -0800 | [diff] [blame] | 2830 | return -EINVAL; |
Pierre Peiffer | c19384b | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 2831 | |
| 2832 | t = timespec_to_ktime(ts); |
Eric Dumazet | 34f01cc | 2007-05-09 02:35:04 -0700 | [diff] [blame] | 2833 | if (cmd == FUTEX_WAIT) |
Thomas Gleixner | 5a7780e | 2008-02-13 09:20:43 +0100 | [diff] [blame] | 2834 | t = ktime_add_safe(ktime_get(), t); |
Pierre Peiffer | c19384b | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 2835 | tp = &t; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2836 | } |
| 2837 | /* |
Darren Hart | 52400ba | 2009-04-03 13:40:49 -0700 | [diff] [blame] | 2838 | * requeue parameter in 'utime' if cmd == FUTEX_*_REQUEUE_*. |
Andreas Schwab | f54f098 | 2007-07-31 00:38:51 -0700 | [diff] [blame] | 2839 | * number of waiters to wake in 'utime' if cmd == FUTEX_WAKE_OP. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2840 | */ |
Andreas Schwab | f54f098 | 2007-07-31 00:38:51 -0700 | [diff] [blame] | 2841 | if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE || |
Darren Hart | ba9c22f | 2009-04-20 22:22:22 -0700 | [diff] [blame] | 2842 | cmd == FUTEX_CMP_REQUEUE_PI || cmd == FUTEX_WAKE_OP) |
Ingo Molnar | e2970f2 | 2006-06-27 02:54:47 -0700 | [diff] [blame] | 2843 | val2 = (u32) (unsigned long) utime; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2844 | |
Pierre Peiffer | c19384b | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 2845 | return do_futex(uaddr, op, val, tp, uaddr2, val2, val3); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2846 | } |
| 2847 | |
Heiko Carstens | 03b8c7b | 2014-03-02 13:09:47 +0100 | [diff] [blame^] | 2848 | static void __init futex_detect_cmpxchg(void) |
| 2849 | { |
| 2850 | #ifndef CONFIG_HAVE_FUTEX_CMPXCHG |
| 2851 | u32 curval; |
| 2852 | |
| 2853 | /* |
| 2854 | * This will fail and we want it. Some arch implementations do |
| 2855 | * runtime detection of the futex_atomic_cmpxchg_inatomic() |
| 2856 | * functionality. We want to know that before we call in any |
| 2857 | * of the complex code paths. Also we want to prevent |
| 2858 | * registration of robust lists in that case. NULL is |
| 2859 | * guaranteed to fault and we get -EFAULT on functional |
| 2860 | * implementation, the non-functional ones will return |
| 2861 | * -ENOSYS. |
| 2862 | */ |
| 2863 | if (cmpxchg_futex_value_locked(&curval, NULL, 0, 0) == -EFAULT) |
| 2864 | futex_cmpxchg_enabled = 1; |
| 2865 | #endif |
| 2866 | } |
| 2867 | |
Benjamin Herrenschmidt | f6d107f | 2008-03-27 14:52:15 +1100 | [diff] [blame] | 2868 | static int __init futex_init(void) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2869 | { |
Heiko Carstens | 63b1a81 | 2014-01-16 14:54:50 +0100 | [diff] [blame] | 2870 | unsigned int futex_shift; |
Davidlohr Bueso | a52b89e | 2014-01-12 15:31:23 -0800 | [diff] [blame] | 2871 | unsigned long i; |
| 2872 | |
| 2873 | #if CONFIG_BASE_SMALL |
| 2874 | futex_hashsize = 16; |
| 2875 | #else |
| 2876 | futex_hashsize = roundup_pow_of_two(256 * num_possible_cpus()); |
| 2877 | #endif |
| 2878 | |
| 2879 | futex_queues = alloc_large_system_hash("futex", sizeof(*futex_queues), |
| 2880 | futex_hashsize, 0, |
| 2881 | futex_hashsize < 256 ? HASH_SMALL : 0, |
Heiko Carstens | 63b1a81 | 2014-01-16 14:54:50 +0100 | [diff] [blame] | 2882 | &futex_shift, NULL, |
| 2883 | futex_hashsize, futex_hashsize); |
| 2884 | futex_hashsize = 1UL << futex_shift; |
Heiko Carstens | 03b8c7b | 2014-03-02 13:09:47 +0100 | [diff] [blame^] | 2885 | |
| 2886 | futex_detect_cmpxchg(); |
Thomas Gleixner | a0c1e90 | 2008-02-23 15:23:57 -0800 | [diff] [blame] | 2887 | |
Davidlohr Bueso | a52b89e | 2014-01-12 15:31:23 -0800 | [diff] [blame] | 2888 | for (i = 0; i < futex_hashsize; i++) { |
Dima Zavin | 732375c | 2011-07-07 17:27:59 -0700 | [diff] [blame] | 2889 | plist_head_init(&futex_queues[i].chain); |
Thomas Gleixner | 3e4ab74 | 2008-02-23 15:23:55 -0800 | [diff] [blame] | 2890 | spin_lock_init(&futex_queues[i].lock); |
| 2891 | } |
| 2892 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 2893 | return 0; |
| 2894 | } |
Benjamin Herrenschmidt | f6d107f | 2008-03-27 14:52:15 +1100 | [diff] [blame] | 2895 | __initcall(futex_init); |